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Quercus  alba  (white  oak) :  cross  section  through  one  entire  growth  ring  and 
portions  of  two  others.  Note  large  pores  in  early  wood  filled  with  tyloses  and 
abruptly  diminishing  in  size  toward  late  wood.  Small  pores  thin-walled  and  in 
lan-like  groups.  Note  "dipping  in"  of  the  outline  of  the  growth  ring  where  it 
crosses  the  large  ray  at  the  right       X  35. 


Identification 


OF    THE 


Economic    Woods    of    the 
United    States 


Including  a  discussion  of  the 

Structural  and  Physical 

Properties  of  Wood 


BY 

Samuel  J.  Record,  M.A.,  M.F. 

Professor  of  Forest  Products,  Yale  University 


SECOND   EDITION 
REVISED    AND    ENLARGED 


NEW   YORK 
JOHN    WILEY    &    SONS,    Inc. 

London  :    CHAPMAN   &    HALL,    Limited 
1919 


BY  THE  SAME  AUTHOR 
Mechanical  Properties  of  Wood. 

viii  -f-  167  pages,  6X9,  51  figures,  22  tables 
Cloth,  $2.50net. 


Copyright,  1912,  1919 
By  Samuel  J.  Record 


Stanbope  jpress 

GILSON    COMPANY 
BOSTON,  U.S.A. 


CONTENTS 


PAGE 

Introduction 1 


PART  I 

Structural  and  Physical  Properties  of  Wood: 

General 5 

Pith 7 

Bark 8 

Primary  wood .11 

Cambium 12 

Secondary  wood 12 

Vessels 14 

Tracheids 16 

Wood  fibres 18 

Wood  parenchyma 21 

Rays 23 

Resin  ducts 29 

Pits 31 

Tyloses 35 

Pith  flecks  or  medullary  spots           .......  36 

Trabecular:  Sanio's  beams       .                 38 

"  Ripple  marks " 39 

Growth  rings 40 

Heartwood  and  sapwood 44 

Grain  and  texture 46 

Knots 48 

Density  and  weight 49 

Water  content  of  wood 52 


IV  CONTENTS 

PAGE 

Shrinkage,  warping,  and  checking 56 

Hygroscopicity 59 

Permeability 60 

Conductivity 62 

Resonance        ...........  62 

Color 64 

Gloss  or  lustre 66 

Scent  or  odor            67 

Taste 69 

Additional  References 69 

PART  II 

Key  to  the  Economic  Woods  of  the  United  States      .         .         .73 

References 109 

Bibliography 119 

Appendix 127 

Index     .,..'..........  147 


ILLUSTRATIONS 


PLATE 

Cross  section  of  Quercus  alba  (white  oak)  ....     Frontispiece 

PLATES 

Map  of  the  United  States  showing  natural  forest  regions  .         .  I 

Photomicrographs  of  wood  sections    .......       II-VI 

TEXT  ILLUSTRATIONS 

Fig.  page 

1.  Cross  sections  of  stem  of  Quercus  prinus  (chestnut  oak)     ...       6 

2.  Typical  wood  cells 19 

3.  Radial  sections  of  heterogeneous  rays         ......     24 

4.  Radial  section  of  ray  of  Pinus  strobus  (white  pine)     .         .         .         .25 

5.  Radial  section  of  ray  of  Pinus  edulis  (pinon  pine)      .         .         .         .26 

6.  Radial  section  of  ray  of  Pinus  resinosa  (red  pine)       .         .         .         .27 

7.  Radial  section  of  ray  of  Pinus  palustris  (longleaf  pine)       .         .         .28 

8.  Cross  section  through  portions  of  two  growth  rings  of  Pinus  ponderosa 

(western  yellow  pine)  ........     30 

9.  Tangential  section  of  fusiform  ray  of  Pinus  ponderosa  (western  yellow 

pine) 31 

10.  Cross  section  of  a  wound  area  of  Tsuga  canadensis  (eastern  hemlock)     32 

11.  Schematic  representation  of  pits 33 

12.  Bars  of  Sanio  in  Pinus  murrayana  (lodgepole  pine)    .         .         .         .38 

13.  Cross  section  through  three  entire  growth  rings  of  Quercus  macrocarpa 

(bur  oak) 42 

14.  Cross  section  through  one  entire  growth  ring  and  parts  of  two  others 

of  Quercus  macrocarpa  (bur  oak)  .         .         .         .         .         .42 

15.  Effects  of  shrinkage 57 


TABLES 

NO.  PAGE 

I.   Length  of  tracheids  in  coniferous  woods 17 

II.   Length  of  wood  fibres  in  dicotyledonous  woods      .         .         .         .20 

III.  One  hundred  and  fifty  trees  of  the  United  States  arranged  in  the 

order  of  the  average  specific  gravity  of  their  dry  woods  .     50 

IV.  Shrinkage  of  wood  along  different  dimensions        .         .         .         .57 
V.   Important  families  and  genera  of  Dicotyledons  in  the  United  States  129 

VI.   Numerical  conspectus  of  the  trees  of  the  United  States        .         .129 

VII.   Indigenous  woods  with  vessel  perforations  exclusively  or  predomi- 
nantly simple 135 

VIII.    Indigenous  woods  with  vessel  perforations  exclusively  scalariform  136 

IX.   Indigenous  woods  with  spiral  markings  in  part  or  all  of  the  vessels  138 

X.   Nature  of  pitting  of  vessel  wall  where  in  contact  with  ray  paren- 
chyma              .        .         .        .        .  139 

XI.   Occurrence  of  tyloses  and  gum  deposits  in  vessels  of  indigenous 

woods 141 

XII.  Families  with  indigenous  representatives  exclusively  diffuse-porous  143 

XIII.  Indigenous  ring-porous  woods 143 

XIV.  Nature  of  pitting  in  wood  fibres  of  indigenous  woods     .        .        .144 
XV.  Kinds  of  rays  in  indigenous  dicotyledonous  woods         .         .         .145 

XVI.    Indigenous  woods  with  "  ripple  marks."  .....  146 


PREFACE  TO  THE  SECOND  EDITION 

The  chief  differences  between  this  edition  and  the  first  (1912) 
are  as  follows:  (1)  The  Key  has  been  entirely  rewritten  and  re- 
arranged, several  new  woods  are  included  and  more  of  the  common 
names  are  given;  (2)  the  lists  of  references  and  the  general  bibli- 
ography have  been  brought  up  to  date;  (3)  an  Appendix  has  been 
added  which  amplifies  some  of  the  subject  matter  of  Part  I,  and 
also  includes  considerable  new  data  on  wood  structure. 

In  grouping  the  woods  in  the  Key  more  attention  has  been 
given  to  their  general  similarity  than  to  special  features,  thus 
bringing  together  for  effective  contrast  the  kinds  which  are  most 
likely  to  be  confused  in  practice.  Attempt  has  been  made  to  have 
all  of  the  descriptions  comparable  and,  so  far  as  permissible,  to 
make  the  gross  characters  the  basis  for  separation.  The  micro- 
scopic features  are  "printed  in  smaller  type  than  the  others,  to 
avoid  confusion  and  to  simplify  the  use  of  the  Key. 

It  is  comparatively  easy  to  make  a  key  for  a  given  lot  of  wood 
specimens,  but  to  take  into  account  the  range  of  variation  of  each 
wood  is  an  extremely  difficult  task.  Such  a  key  must  be  the  re- 
sult of  growth,  of  the  accumulation  of  years  of  investigation  and 
experience,  and  must  always  be  subject  to  revision  as  new  data 
and  new  material  become  available.  To  this  end  the  author 
would  enlist  the  cooperation  of  all  readers  of  this  book. 

Samuel  J.  Record. 


INTRODUCTION 


As  the  available  supply  of  the  standard  kinds  of  timber  has 
decreased,  woods  have  appeared  on  the  market  which  formerly 
were  considered  worthless.  In  some  instances  the  new  woods  are 
sold  under  their  own  names,  but  usually  they  are  employed  as 
substitutes  for  more  expensive  kinds,  or  sold  in  indiscriminate 
mixture.  It  thus  becomes  a  matter  of  great  importance  that 
foresters,  timber-inspectors,  and  wood-users  be  able  to  distinguish 
the  woods  with  which  they  deal.  The  number  of  such  woods  is  so 
large,  and  their  resemblance  often  so  close,  that  one  can  no  longer 
depend  upon  distinguishing  them  through  mere  familiarity  with 
their  general  appearance.  To  identify  woods  it  is  necessary  to 
have  a  knowledge  of  the  fundamental  differences  in  their  structure 
upon  which  the  points  of  distinction  are  based. 

The  literature  bearing  directly  upon  this  subject  is  very 
limited,  and  such  information  as  exists  is  for  the  most  part  dis- 
tributed throughout  a  considerable  number  of  publications  and  not 
readily  available.  Teachers  and  students  of  wood  technology  are 
seriously  handicapped  by  the  lack  of  suitable  text-books  or 
manuals.  It  is  in  an  attempt  to  supply  in  small  part  this  defi- 
ciency that  the  writer  has  prepared  for  publication  a  portion  of  the 
material  given  in  one  of  his  courses  in  Forest  Products  at  the 
Yale  Forest  School.  While  it  is  designed  primarily  as  a  manual 
for  forestry  students,  it  is  hoped  that  it  will  also  aid  others  in  the 
study  and  identification  of  wood. 

Part  I  deals  briefly  with  the  more  important  structural  and 
physical  properties  of  wood.  The  structural  properties  are  based 
upon  the  character  and  arrangement  of  the  wood  elements. 
Under  this  head  are  considered:  (a)  the  external  form  of  the  tree 
in  its  various  parts;  (b)  the  anatomy  of  the  wood;  (c)  abnormal 
developments  or  formations;  (d)  relation  of  these  properties  to 
the  usefulness  of  wood;  and  (e)  their  importance  in  classification. 
The  physical  properties  are  based  upon  the  molecular  composition 
of  the  wood  elements.  Under  this  head  attention  is  given  to 
(a)  the  properties  manifest  to  unaided  senses,  viz.,  color,  gloss. 

1 


2  INTRODUCTION 

odor,  taste,  and  resonance;  (b)  those  determined  by  measurement,. 
viz.,  density,  weight,  water  content,  shrinkage,  swelling,  warping, 
and  hygroscopicity ;  (c)  relation  of  these  properties  to  the  use- 
fulness of  wood;  and  (d)  their  employment  to  some  extent  as  aids, 
to  identification. 

In  Part  II  attempt  is  made  to  use  the  details  of  Part  I  in  the 
construction  of  an  artificial  classification  of  the  economic  woods 
of  the  United  States.  Unimportant  species  have  in  some  cases- 
been  included  where  it  was  felt  that  their  presence  would  not  lead 
to  confusion.  This  classification  has  been  prepared  with  two 
objects  in  view:  (1)  for  use  in  practice  as  a  key  for  the  identifica- 
tion of  unknown  specimens ;  (2)  for  use  in  the  laboratory  as  a  basis 
for  the  comparative  study  of  known  specimens. 

As  far  as  considered  practicable,  the  distinctions  in  the  key 
are  based  on  macroscopic  features,  those  readily  visible  to  the 
unaided  eye  or  with  the  aid  of  a  simple  lens  magnifying  10  to 
15  times.  Owing  to  the  great  variation  of  wood  it  is  usually 
unwise  to  rely  upon  single  diagnostic  features,  and  for  this  reason 
the  descriptions  have  been  extended  to  embrace  all  or  most  of  the 
important  characters  so  far  recognized.  This  method  also  permits 
ready  arrangement  of  the  key  or  the  fitting  into  it  of  additional 
woods. 

In  the  woods  of  many  genera  the  structural  variations  appar- 
ently are  not  sufficiently  distinct  and  constant  to  assure  specific 
identification.  Good  examples  of  this  are  afforded  by  the  woods 
of  Pinus,  Quercus,  Hicoria,  and  Populus,  where  it  is  usually 
difficult  and  very  often  impossible  to  do  more  than  separate  them 
into  groups.  Accurate  knowledge  of  the  botanical  and  com- 
mercial range  of  each  species  will  often  serve  as  a  basis  for  further 
subdivision  of  a  group  in  which  other  distinctions  are  apparently 
wanting. 

In  preparing  a  specimen  for  careful  examination  either  with 
or  without  a  lens  it  is  highly  desirable  that  a  very  smoothly  cut 
surface  be  obtained.  If  the  knife  used  is  not  sharp,  the  cut  surface 
will  be  rough  and  the  details  of  structure  obscured.  Cross  sections 
are,  as  a  rule,  the  most  valuable  for  comparative  study,  and  in 
making  them  it  is  very  important  that  the  plane  of  section  be 
as  nearly  as  possible  at  right  angles  to  the  vertical  axis  of  the 
specimen. 

A  compound  microscope  is  necessary  for  the  study  of  the 
minute  anatomy  of  wood.     Sections  for  immediate  observation 


INTRODUCTION  3 

may  be  cut  free-hand  with  a  sharp  pocket-knife  or  razor  and 
mounted  in  water.  To  avoid  air  bubbles  in  the  sections  small 
pieces  of  the  specimens  should  be  boiled  prior  to  sectioning. 
It  is  not  important  that  such  sections  be  of  uniform  thickness, 
since  a  thin  edge  will  usually  exhibit  the  essential  details- 
Much  better  results  can  be  obtained  by  the  use  of  a  microtome. 
Penhallow  recommends  a  table  microtome  and  a  plane  blade 
mounted  in  a  heavy  wooden  handle  of  such  a  form  as  to  provide  a 
perfectly  firm  grip.  For  fine  work,  however,  a  sliding  microtome 
specially  constructed  for  sectioning  wood  is  best.  Success  depends 
largely  upon  the  sharpness  of  the  knife  and  the  rigidity  of  the 
apparatus. 

Considerable  care  should  be  exercised  in  the  selection  of 
material  for  sectioning.  Small  blocks  of  about  a  quarter-inch  cube 
should  be  cut  from  green  material,  or  from  the  interior  of  dry 
pieces.  The  faces  of  the  blocks  should  represent  sections  which 
are  as  nearly  cross,  radial,  and  tangential  as  possible.  Blocks  of 
the  lighter  woods  can  be  softened  sufficiently  by  boiling  them  in 
water  until  thoroughly  saturated.  The  process  may  be  hastened 
by  interrupting  the  boiling  by  additions  of  cold  water.  In  the 
case  of  the  harder  woods,  however,  it  is  a  good  plan  to  place 
the  small  blocks,  after  boiling,  in  a  solution  of  hydrofluoric  acid 
for  a  period  varying  from  ten  days  to  three  weeks,  the  strength 
of  solution  and  the  duration  of  immersion  depending  upon  the 
hardness  of  the  wood.  After  removal  from  the  acid  the  blocks 
should  be  thoroughly  washed  and  then  placed  for  several  days  in 
glycerine,  after  which  they  are  ready  for  sectioning.  The  sections 
may  either  be  mounted  unstained  in  glycerine  or  stained  in  the 
usual  way  and  mounted  in  balsam.  For  ordinary  work  unstained 
glycerine-mounts  afford  the  most  satisfactory  results,  since  the 
natural  colors  are  preserved.  (For  more  detail,  see  references 
below.) 

References 

Bailey,  I.  W.:  Microtechnique  for  Woody  Structures,  Bot.  Gaz.,  Vol.  XLIX, 

Jan.  1910,  pp.  57-58. 
Plowman,  A.  B.:  The  Celloiden  Method  with  Hard  Tissues,  Bot.  Gaz.,  Vol. 

XXXVII,  June  1904,  pp.  456-461. 
Penhallow,  D.  P. :  North  American  Gymnosperms,  Boston,  1907,  pp.  16-23. 
Benedict,  H.  M.:  An  Imbedding  Medium  for  Brittle  or  Woody  Tissues, 

Bot.  Gaz.,  Vol.  LII,  Sept.  1911,  p.  232. 
Thompson,  R.  B.:  A  Modification  of  a  Jung-Thoma  Sliding  Microtome  for 

Cutting  Wood,  Bot.  Gaz.,  Vol.  L,  Aug.  1910,  pp.  148-149. 


4  INTRODUCTION 

The  best  idea  of  the  form  and  size  of  the  individual  cells  is 
gained  from  study ing  macerated  material.  This  is  readily  obtained 
by  placing  small  pieces  of  wood  in  a  test-tube  together  with  a 
number  of  crystals  of  potassium  chlorate,  and  adding  enough 
nitric  acid  to  cover  them  well.  After  the  wood  has  turned  white 
the  solution  should  then  be  poured  off  and  the  material  washed 
thoroughly  in  water.  This  action  may  be  hastened  by  warming. 
It  is  then  easy  to  remove  a  small  portion  of  the  mass  to  a  slide 
where  it  can  be  dissected  with  a  couple  of  needles  and  studied 
under  the  microscope. 

The  writer  desires  to  acknowledge  his  indebtedness  to  Prof. 
James  W.  Tourney  for  much  of  the  da.ta  upon  which  this  work  is 
based;  to  Mr.  Clayton  D.  Mell  for  many  helpful  suggestions  and 
criticisms;  and  to  Mr.  Charles  J.  Heller  for  the  loan  of  a  set  of 
wood  sections  from  which  the  photo-micrographs  were  made 
by  the  writer  at  the  Forest  Products  Laboratory,  Madison,  Wis- 


PART  I 

STRUCTURAL    AND    PHYSICAL   PROPERTIES 
OF   WOOD 


Wood  of  a  timber-producing  tree  may  be  considered  under 
three  general  heads,  viz.,  root,  stem,  and  branch.  The  relative 
proportion  of  the  three  classes  of  wood  in  a  tree  depends  on  the 
species,  the  age,  and  the  environmental  conditions  of  growth. 
The  woody  portion  of  stem  and  branch  has,  within  certain  limits, 
the  same  structure.  Branches  are  of  less  technical  value  because 
of  their  irregular  shape  and  small  dimensions.  The  latter  is  due 
to  the  fact  that  the  number  and  thickness  of  the  layers  of  growth 
are  less  and  the  wood  elements  smaller  than  in  the  bole. 

Wood  of  roots  always  differs  somewhat  from  that  of  the  stem 
in  form,  structure,  and  distribution  of  the  elements;  the  growth 
rings  are  narrower,  the  elements  have  wider  lumina,  and  the 
wood  is  as  a  rule  lighter,  softer,  and  more  porous.  Roots,  with 
occasional  exceptions,  are  a  very  subordinate  source  of  wood  in 
America. 

Stem  wood,  on  account  of  its  more  desirable  dimensions  and 
shape  and  its  greater  uniformity,  is  of  the  greatest  utility  and 
value.  The  form  and  character  of  the  stem  are  of  greater  impor- 
tance than  the  relative  volume;  with  few  exceptions  the  more 
nearly  straight  and  cylindrical  and  the  freer  from  limbs,  knots, 
and  defects,  the  greater  are  its  technical  properties  and  value. 
These  properties  are  largely  determined  by  the  age  of  the  tree 
and  the  inherent  characteristics  of  the  species,  though  affected 
by  environment.  Straightness  and  clearness  are  materially 
influenced  by  density  of  stand. 

A  woody  stem,  branch,  or  root  is  composed  of  three  unlike 
parts  (Fig.  1).  Through  the  central  portion  runs  a  narrow  cylinder 
of  soft  tissue,  the  pith.  On  the  outside  is  bark.  Between  these 
two  and  making  up  the  bulk  of  the  structure  is  the  wood  or  xylem. 
The  wood,  particularly  in  old  sections,  usually  shows  a  central 

5 


6 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


colored  portion,  the  heartwood,  and  a  nearly  colorless  outer  border, 
the  sapwood.  In  fresh-cut  green  sections  the  sapwood  is  further 
differentiated  by  its  greater  moisture  content. 

Indigenous  arborescent  plants  are  readily  separable  in  o  two 


Fig.  1. — Cross  section  of  stem  of  Quercus  prinus  (chestnut  oak);  b,  bark 
showing  outer  and  inner  portions;  s.  w.,  sapwood;  the  darker  inner  portion  is 
heartwood;  a.  r.,  annual  or  growth  ring;  p.  r.,  (pith)  ray,  a  large  number  of  which 
can  be  seen  crossing  the  growth  rings  at  right  angles.  Note  season  checks.  Natural 
size.    (From  Bui.  102,  U.  S.  Forest  Service.) 


great  natural  classes:  I,  Gymnosperms,  and  II,  Angiosperms. 
Class  I  is  further  divided  into  two  unequal  groups:  Coniferce  (13 
genera),  and  Taxacece  (2  genera).     Class  II  embraces  (according  to 


ECONOMIC    WOODS   OF   THE   UNITED   STATES  7 

Sargent's  " Manual  of  the  Trees  of  North  America"),  Mono- 
cotyledons (2  families  and  8  genera),  and  Dicotyledons  (62  fam- 
ilies and  162  genera) .  The  Monocotyledons  are  of  comparatively 
slight  importance  as  sources  of  wood,  and  for  that  reason,  as  well 
as  on  account  of  their  peculiar  structure,*  are  omitted  from  the 
general  discussion  of  wood  and  from  the  key. 

The  woods  of  the  Gymnosperms  are  commonly  referred  to  as 
''coniferous  woods,"  "softwoods,"  and  " needle-leaved  woods." 
These  terms  are  inexact  since  (1)  the  Taxacece  do  not  bear  cones; 
(2)  many  of  the  so-called  "softwoods"  (e.g.,  Pinus  palustris, 
Pseudotsuga,  Taxus)  are  harder  than  many  of  the  so-called  "hard 
woods"  {e.g.,  Populus,  Salix,  JEsculus,  Tilia);  and  (3)  the  con- 
trast in  the  leaves  is  by  no  means  always  as  great  as  the  terms 
"needle"  and  "broad"  would  indicate.  Common  usage,  how- 
ever, has  given  these  names  sufficient  definiteness  for  ordinary 
purposes,  though  they  should  be  avoided  where  scientific  exact- 
ness is  desired. 

PITH 

The  central  portion  of  the  young  shoot,  branch,  and  root  is 
composed  of  loosely  aggregated,  mostly  thin-walled,  isodiametric, 
parenchymatous  cells — the  pith.  It  is  usually  of  small  diameter, 
does  not  increase  in  size  after  the  first  year,  in  fact,  may  even  in 
some  instances  be  compressed,  and  appears  to  be  of  only  temporary 
utility  to  the  tree.  In  some  cases,  according  to  Gris  (loc.  tit.), 
the  cells  remain  active  for  several  years,  and  alternately  store 
and  give  up  products  of  assimilation,  especially  starch  and  tannin, 
according  to  the  periods  of  vegetation.  In  such  instances  the 
walls  of  the  active  cells  are  thickened  and  densely  pitted. 

The  pith  in  woody  stems  of  Gymnosperms  is  fairly  uniform  in 
shape,  size,  color,  and  structure;  in  Dicotyledons  there  is  great 
variation.  As  to  outline  in  cross  section:  it  is  star-shaped  in 
Quercus,  triangular  in  Fagus,  Betula,  and  Alnus;  ovoid  in  Tilia, 
Fraxinus,  and  Acer;  circular  in  Juglans,  Ulmus,  and  Cornus. 
In  Juglans  the  color  is  black;  in  Gymnocladus  it  is  red;  in  many 
others  it  is  brown  or  gray.     In  Rhus,  Sambucus,  and  Ailanthus  the 

*  In  adult  steins  of  Monocotyledons  the  fibro-vascular  bundles  are  scat- 
tered throughout  the  central  cylinder  instead  of  being  disposed  in  a  circle, 
as  in  the  Dicotyledons.  The  bundles  are  closed  and  the  tracheary  tissue 
surrounds  the  phloem. 


8  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

pith  is  comparatively  large  and  conspicuous,  often  deeply  colored. 
In  Magnolia,  Liriodendron,  Nyssa,  Asimina,  and  Anona  there  is 
often  a  more  or  less  distinct  septation  of  the  continuous  pith 
by  plates  of  stone  cells,  while  in  Juglans  there  is  decided  septation 
but  the  diaphragms  are  not  sclerotic,  and  the  pith  is  not  con- 
tinuous between  the  disks.  On  account  of  these  and  other  pecu- 
liarities the  pith  when  present  in  a  specimen  of  wood  is  frequently 
an  aid  to  identification. 

References 

DeBary,  A.:  Comparative  Anatomy,  Oxford,  1884,  pp.  402-403;   533-534. 
Foxworthy,  J.  W.:   Discoid  Pith  in  Woody  Plants,  Proc.  Indiana  Academy 

of  Science  for  1903,  Indianapolis,  1904,  pp.  191-194. 
Solereder,  Hans:  Systematic  Anatomy  of  the  Dicotyledons,  Oxford,   1908, 

pp.  133-134. 
Gris,   A.:    Sur  la  Moelle   des  Plantes  Ligneuses,   Amer.   Sci.  Nat.,  Ser.  5, 

Tome  XIV,  1872. 


Bark  is  the  name  commonly  applied  to  that  portion  of  a 
stem  lying  outside  the  cambium  layer.  Used  in  this  broad  sense, 
it  is  customary  to  distinguish  an  outer  (dry)  portion  and  an  inner 
(living)  portion.  The  structure  of  bark  is  highly  complex  and 
widely  variable. 

When  shoots  are  first  formed  they  are  covered  by  a  very 
thin  layer  of  tissue,  the  epidermis.  Beneath  this  is  the  primary 
cortex  and  the  pericycle.  The  latter  is  commonly  composed  of  two 
kinds  of  tissues,  thin-walled  parenchyma  and  bast-fibres.  The  bast- 
fibres  may  occur  in  isolated  groups  or  form  a  continuous  band 
around  the  stem.  When  in  groups  they  are  often  closely  associated 
with,  but  not  really  part  of,  the  phloem  of  the  vascular  bundles. 
Bast-fibres  are  attenuated  sclerenchymatous  elements,  with 
sharp  ends  simple  or  branched.  Their  function  is  to  give 
strength  to  the  stem  and  to  protect  the  delicate  tissues  of  the 
phloem.  It  is  to  them  that  many  barks  owe  their  great  tough- 
ness and  pliability. 

Phloem,  which  is  the  outer  portion  of  a  vascular  bundle,  is  in 
typical  cases  composed  of  sieve  tubes,  companion  cells,  and  phloem 
parenchyma.  In  structure  sieve  tubes  resemble  vessels,  but  their 
walls  are  mostly  delicate,  non-lignified,  colorless,  cellulose  mem- 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  9 

branes.  Between  the  ends  of  the  sieve-tube  segments  (and  some- 
times between  adjacent  side  walls  as  well)  are  thin  plates  dotted 
with  pits,  resembling  a  sieve.  The  pit  membranes  are  finally 
absorbed,  allowing  free  communication  from  one  cell  to  another. 
Unlike  vessels,  the  segments  of  the  sieve  tubes  remain  alive  for  a 
year  or  more,  though  they  lose  their  nuclei.  This  unusual  phe- 
nomenon may  be  due  to  some  influence  of  the  companion-cells 
or  to  associated  parenchyma  cells.  The  function  of  the  sieve 
tubes  is  the  vertical  (especially  downward)  distribution  of  elab- 
orated food  materials.  After  the  first  year  the  cells  usually  be- 
come crushed  by  the  pressure  of  the  surrounding  tissues,  their 
places  being  taken  by  new  cells  generated  by  the  cambium. 

In  addition  to  the  structure  just  mentioned,  many  other 
elements  and  structures  may  enter  the  composition  of  the  bark. 
Among  these  may  be  mentioned  resin  ducts,  latex  tubes,  stone  cells, 
crystals,  mucilage  sacs,  and  tannin  sacs.  Bast  rays  are  also  present, 
being  continuous  with  the  rays  of  the  xylem.  They  increase  in 
width  uniformly  and  gradually  as  they  recede  from  the  cambium. 

In  practically  all  cases  of  growth  in  thickness  the  epidermis 
is  destroyed  at  an  early  period  and  is  replaced  by  cork.  Cork  is 
suberised  tissue  formed  by  a  special  meristem  called  cork  cambium 
or  phellogen,  which  originates  in  the  epidermis  or  in  the  cells  just 
beneath  the  epidermis.  All  parenchymatous  cells,  however, 
wherever  located,  appear  to  possess  the  ability  to  form  cork. 
Wound  surfaces  are  closed  and  healed  by  it,  and  diseased  and 
dead  parts  are  isolated  from  those  in  living  condition. 

The  formation  of  cork  cambium  in  the  bark  usually  occurs 
during  the  first  year's  growth  of  the  stem.  As  a  result  of  its 
activity  a  layer  of  cork  cells  is  generated  on  the  outside,  and  fre- 
quently a  layer  of  thin-walled  parenchyma  cells — the  phelloderm — 
on  the  inside.  Collectively  these  new  tissues,  including  the  cork 
cambium,  are  called  the  periderm.  The  effect  of  the  development 
of  cork  is  to  cut  off  from  the  interior  mass  of  tissue  portions  of  the 
cortex,  which  dry  up  and  are  eventually  thrown  off  as  outer  bark. 
This  action  may  occur  only  once,  as  in  Fagus  and  Carpinus,  but 
usually  is  repeated,  and  successively  deeper  layers  of  the  cortex 
and  eventually  of  the  pericycle  and  phloem  are  cut  off. 

In  some  species  the  successive  formations  of  cork  extend 
more  or  less  uniformly  around  the  stem,  cutting  off  in  each  case 
an  annular  layer  of  cortex — sometimes  called  ring  bark.  In  other 
species  the  successive  internal  layers  are  very  irregular,  and  cut 


10  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

off  scale-like  portions  of  the  cortex — scale-bark.  The  results  are 
subject  to  very  wide  variation. 

In  Platanus  and  Taxus  the  outer  bark  is  shed  annually  in 
the  form  of  comparatively  large,  irregular,  thin  flakes  which,  falling 
away,  leave  the  surface  smooth.  In  species  of  Betula  thin,  exfoli- 
ating layers  are  produced,  marked  with  horizontal  lines  of  lenticels. 
In  many  species  of  Pinus,  the  outer  bark  of  mature  trees  is  made 
up  of  small,  irregular  scales  in  very  intricate  pattern.  In  Hicoria 
ovata  and  H .  laciniosa  the  outer  bark  peels  off  in  long,  flat,  reddish- 
brown  strips,  while  several  other  species  of  the  same  genus  have 
bark  that  is  not  flaky.  In  a  great  many  woody  plants  the  layers 
of  bark  persist  for  many  years,  and,  as  the  stem  increases  in  size, 
become  more  and  more  cracked  and  furrowed.  Such  is  the  case 
in  Quercus,  Robinia,  Liriodendron,  etc.  In  Sequoia,  Juniperus, 
Taxodium,  and  others  of  the  Cedar  group,  the  bark  is  character- 
istically fibrous.  These  examples  are  sufficient  to  indicate  the  wide 
variation  in  the  bark  and  its  importance  as  an  aid  to  the  identi- 
fication of  a  specimen  upon  which  any  portion  of  bark  remains. 

The  bark  of  many  trees  is  of  high  technical  value.  A  very 
great  number  are  used  for  medicinal  purposes.  Tsuga  and  species 
of  Quercus  possess  barks  which  contribute  very  largely  to  our 
tannin  supply,  upon  which  the  leather  industry  is  dependent. 
Some  barks  contain  coloring  principles;  others  (e.g.,  Hicoria  ovata) 
are  highly  valuable  for  fuel.  Birch  bark  was  formerly  used  for 
canoes.  The  inner  barks  of  some  woods  (e.g.,  Tilia)  are  sometimes 
used  in  manufacturing  fibre  cloth.  The  highly-developed  corky 
layers  of  Quercus  suber  furnish  the  cork  of  commerce. 

References 

Stevens,  W.  C:  Plant  Anatomy,  Philadelphia,  1907,  pp.  37-39;  56-58;  72-82. 

DeBary,  A.:  Comparative  Anatomy,  pp.  108-114;    519-566. 

Sachs,  Julius:  Text-Book  of  Botany,  Oxford,  1875,  pp.  90-92. 

Gregory,  E.  L.:  Elements  of  Plant  Anatomy,  Boston,  1895,  pp.  133-142. 

Henkel,  Alice:  American  Medicinal  Barks,  Bui.  139,  U.  S.  Bu.  Plant 
Industry,  1909,  p.  59. 

Hill,  Arthur  W. :  Sieve-Tubes  of  Gymnosperms,  Annals  of  Botany,  Vol. 
XV,  Dec.  1901. 

:  Notes  on  the  Histology  of  the  Sieve-tubes  of  Certain  Angiosperms, 

Annals  of  Botany,  Vol.  XVII,  Jan.  1903,  pp.  265-267. 

Moeller,  Joseph:  Anatomie  der  Baumrinden;  Vergleichende  Studien,  Ber- 
lin, 1882,  p.  447. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES  11 


PRIMARY   WOOD 

At  the  growing  apex  of  a  stem  is  an  undifferentiated  tissue 
composed  of  very  thin-walled  cells  essentially  all  alike.  This  tissue 
is  known  as  the  'primordial  meristem. 

Below  the  apex  the  primordial  meristem  becomes  differentiated 
into  three  distinct  parts,  viz.,  (1)  the  protoderm  at  the  outside, 
(2)  the  procambium  strands,  and  (3)  the  fundamental  or  ground 
meristem.  These  three  regions  or  tissues  are  themselves  subject  to 
further  differentiation  and  are  called  primary  meristems.  The 
protoderm  changes  into  the  epidermis;  the  ground  meristem  into 
pith,  primary  rays,  pericycle,  and  primary  cortex;  the  pro- 
cambium  strands  into  vascular  bundles,  which  are  disposed  in  a 
circle  around  the  pith  and  separated  from  each  other  by  the 
primary  rays.  The  vascular  bundles  are  composed  of  three  parts, 
an  inner  called  the  xylem,  an  outer  called  the  phloem,  and,  separ- 
ating the  two,  a  thin  layer  of  generative  tissue,  the  cambium. 
These  tissues,  being  the  direct  development  of  the  cells  of 
the  procambium,  are  termed  primary  (primary  wood  —  proto- 
xylem  and  metaxylem  —  and  primary  phloem),  in  contradistinction 
to  the  tissues  generated  by  the  cambium,  which  are  termed 
secondary. 

Primary  wood  is  relatively  unimportant,  though  of  scientific 
interest  because  of  its  peculiar  structure,  which  in  many  ways 
differs  from  the  other  wood  of  the  stem.  Thus  in  Angiosperms, 
wood  fibres  are  usually  wanting  and  tracheids  are  not  common 
in  the  primary  wood,  while  in  the  secondary  wood  fibres  are 
always  present  and  tracheids  commonly  so.  In  Gymnosperms  the 
vascular  elements  of  the  primary  wood  are  indeterminate  in 
length,  marked  with  spirals  and  for  the  most  part  devoid  of  pits 
in  their  walls,  while  the  corresponding  elements  in  the  secondary 
wood  are  of  determinate  length,  rarely  marked  with  spirals  and 
always  pitted. 

References 

Stevens,  William  C:  Plant  Anatomy,  pp.  25-45. 
Penhallow,  D.  P. :  North  American  Gymnosperms,  pp.  38,  40. 
DeBary,  A.:  Comparative  Anatomy,  p.  321. 
Sachs,  J.:  Text-Book  of  Botany,  p.  574. 


12  ECONOMIC   WOODS   OF   THE   UNITED    STATES 


CAMBIUM 

As  previously  stated,  that  portion  of  a  pro-cambium  strand 
which  remains  capable  of  division  and  generation  is  known  as 
fascicular  (i.e.,  bundle)  cambium,  since  it  produces  on  the  inner 
side  wood  or  xylem,  and  on  the  outer  phloem — collectively  a  fibro- 
vascular  bundle.  The  cambia  of  the  several  bundles  are  later 
united  into  a  continuous  sheath,  and  the  portion  between  the 
original  bundles  is  termed  the  inter-fascicular  cambium.  The 
cambial  layer  sheathes  the  entire  woody  cylinder  from  root  to 
branch  and  separates  it  from  the  cortex  or  bark.  It  is  composed 
of  a  thin  layer  of  delicate,  thin-walled,  vertically  elongated  cells 
filled  with  protoplasm  and  plant  food.  It  is  this  layer  that  is 
torn  when  bark  is  stripped  from  a  living  tree.  During  vigorous 
growth,  "when  the  sap  is  up,"  the  cells  of  the  cambium  are  par- 
ticularly delicate,  a  fact  taken  advantage  of  in  peeling  poles,  logs, 
and  basket-willow  rods. 

The  division  and  development  of  the  cambial  cells  give  rise 
to  (a)  a  layer  of  new  wood  on  the  outside  of  that  last  produced; 
(6)  a  layer  of  new  phloem  on  the  inside  of  that  last  produced ;  (c) 
continuation  of  the  medullary  rays  of  both  xylem  and  phloem; 
and  (d)  new  cambium. 

/ 
References 

DeBary,  A.:  Comparative  Anatomy,  pp.  454-475. 

Bailey,  I.  W.:  Relation  of  Leaf -Trace  to  Compound  Rays  in  Lower  Dicoty- 
ledons, Annals  of  Botany,  Vol.  XXV,  No.  97,  June  1911. 

Rubner,  Konrad:  Das  Hungern  des  Cambiums  und  das  Aussetzen  der 
Jahfringe,  Naturw.  Zeitschrift  fur  Forst-  und  Landwirtschaft,  8.  Jahr- 
gang,  1910,  pp. 212-262. 

Von  Mohl,  Hugo:  Ueber  die  Cambiumschicht  des  Stammes  der  Phanero- 
gamen  und  ihr  Verhaltniss  zum  Dickenwachsthum  desselben,  Bot. 
Zeitung,  Vol.  XVI,  1858,  pp.  183-198. 


SECONDARY   WOOD 

Tissues  formed  from  cambium  are  termed  secondary.  Almost 
all  of  the  wood  of  a  stem  is  secondary  wood,  the  small  amount  of 
primary  wood  being  wholly  negligible  from  a  technological  point  of 
^iew. 

The  principal  functions  of  secondary  wood  are  (a)  to  provide 


ECONOMIC   WOODS   OF   THE   UNITED   STATES 


13 


mechanical  support  for  the  tree;  (6)  to  afford  means  for  the  ascent 
of  sap  from  the  roots  to  the  foliage;  (c)  alternately  to  store  up 
and  to  give  back  products  of  assimilation,  particularly  starch. 

While  the  elements  of  secondary  wood  are  subject  to  wide 
variation,  they  may  for  convenience  be  referred  to  three  principal 
types,  viz.,  (1)  vascular,  (2)  fibrous,  (3)  parenchymatous.  Between 
these  groups  are  transitional  and  specialized  forms  whose  reference 
to  one  or  the  other  of  these  groups  is  often  purely  arbitrary.  The 
classification  may  be  extended  as  follows: 


Vascular  elements 
True  vessels 
Tracheids 

(wood)  tracheids 
ray  tracheids 


Fibrous  elements 

Wood  fibres 

Septate  wood  fibres 
Parenchymatous  elements 

Wood  parenchyma 

Ray  parenchyma 


In  the  following  table  are  shown  side  by  side  the  important 
differences  in  the  distribution  of  the  elements  in  typical  secondary 
wood  of  Gymnosperms  and  Dicotyledons.     (See  Appendix,  p.  131.) 


Gymnosperms 
True  vessels  absent. 
Wood  tracheids  present  and  forming 

bulk  of  wood. 
Ray  tracheids  present  or  absent. 
Wood  fibres  absent. 
Wood  parenchyma  present  (except  in 

Taxacece),  but  usually  subordinate. 
Ray  parenchyma  present. 


Dicotyledons 
True  vessels  present. 
Tracheids  present  or  absent;   always 

subordinate. 
Ray  tracheids  absent. 
Wood  fibres  present. 
Wood  parenchyma  present,  and  very 

often  conspicuous. 
Ray  parenchyma  present. 


From  the  above  it  is  apparent  that  the  wood  of  Dicotyledons 
is  more  heterogeneous  in  its  nature  than  that  of  Gymnosperms, 
which  is  composed  almost  wholly  of  tracheids  and  ray  parenchyma. 


References 

Solereder,  H.:  Anatomy  of  the  Dicotyledons,  Vol.  II,  pp.  1133-1168. 

DeBary,  A.:  Comparative  Anatomy,  pp.  458-500. 

Boulger,  G.  S.:  Wood,  London,  1908,  pp.  1-54. 

Stevens,  W.  C:  Plant  Anatomy,  pp.  48-56;   72-112. 

Sachs,  J.:  Text-Book  of  Botany,  pp.  92-102. 

Mell,  CD.:  A  Confusion  of  Technical  Terms  in  the  Study  of  Wood  Struc- 
ture, For.  Quarterly,  Vol.  IX,  No.  4,  1911,  pp.  574-576. 

:   Classification  of  Woods  by  Structural  Characters,  Am.  Forestry, 

Vol.  XIV,  April  1910,  pp.  241-243. 


14  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

Stone,  H. :  The  Use  of  Anatomical  Characters  in  the  Identification  of  Wood, 

'Nature,  Vol.  LXV,  No.  1686,  1902,  pp.  379-380. 
Gayer,  K.:  Schlich's  Manual  of  Forestry,  Vol.  V,  1908,  pp.  7-19. 
Metzger,  K.:   Ueber  der  Konstructionsprinzip  des  secundaren  Holzkorpers, 

Naturw.    Zeitschrift    fur    Forst-  und    Landwirtschaft,   6.    Jahrgang, 

1908,  pp.  249-273. 
Wieler,  A. :   Ueber  die  Beziehung  zwischen  Wurzel-  und  Staumholz,  Forstw. 

Jahrbuch,  Tharand,  Vol.  XLI,  1891,  pp.  143-171. 
Hartig,  Robert:   Untersuchungen  iiber  die  Entstehung  und  die  Eigenschaf- 

ten  des  Eichenholzes,  Forstlich-naturw.  Zeitschrift,  Vol.  Ill,  1894,  pp. 

1-13;  49-68;  172-191;  193-203. 
Hartig,  Robert,  and  Weber,  Rudolph:  Das  Holz  der  Rothbuche  in  Ana- 

tomisch-physiologischer,  Chemischer  und  Forstlicher  Richtung,  Berlin, 

1888,  pp.  20-28. 
Sanio,  Carl:  Vergleichende  Untersuchungen  uber  die  Elementarorgane  des 

Holzkorpers,  Botanische  Zeitung,  Vol.  XXI,  1863,  pp.  85-128. 
:  Verg.  Unt.  u.  d.  Zusammensetzung  des  Holzkorpers,  Ibid.,  Vol. 

XXI,  1863,  pp.  358-412. 
Wiesner,  Julius:  Die  Rohstoffe  des  Pflanzen  Reiches,  Vol.  II,  Leipzig,  1903, 

pp.  1-35. 

vessels  (see  Appendix,  p.  132) 

Vessels  are  indeterminate,  tube-like  cell-fusions  found  in  the 
wood  of  all  indigenous  dicotyledonous  plants.  In  fact  the  absence 
of  xylem  vessels  in  woody  Dicotyledons  is  a  very  rare  phenomenon 
which,  according  to  Solereder  (loc.  cit.,  p.  1136),  has  been  recorded 
only  in  the  exotic  genera  Drimys  and  Zygogynum  of  the  Mag- 
noliacece,  and  Tetracentron  and  Trochodendron  of  the  Trochoden- 
dracece. 

Vessels  arise  from  cambial  cells  which  increase  in  size  and, 
through  the  partial  or  complete  absorption  of  their  end-walls  at 
the  close  of  the  process  of  thickening,  become  continuous  in  a 
longitudinal  row.  There  is  always  a  constriction  at  the  place  of 
fusion  of  the  cells,  thus  plainly  demarking  the  vessel  segments  (Plate 
VI,  Nos.  3,  4,  6).  The  walls  of  contact  of  the  segments  of  a  ves- 
sel are  sometimes  (a)  horizontal,  but  more  often  (b)  oblique,  and 
fit  together  exactly;  or,  again,  they  may  be  (c)  oblique  with  a  por- 
tion of  the  opposed  faces  united,  the  pointed  and  blind  ends  extend- 
ing beyond  the  division  wall,  as  in  Liquidambar  and  Quercus.  In 
(a)  the  perforation  from  one  segment  to  another  is  simple,  i.e.,  with 
one  round  opening.    In  (6)  and  (c)  the  perforations  are  sometimes 


ECONOMIC   WOODS   OP   THE   UNITED   STATES  15 

simple  and  sometimes,  especially  in  strongly  inclined  division 
walls,  scalariform,  that  is,  the  opening  is  crossed  with  few  to  many 
bars  in  ladder-like  arrangement.  The  bars  are  usually  transverse 
to  the  longitudinal  axis  of  the  vessel.  Both  simple  and  scalari- 
form perforations  may  occur  side  by  side  in  the  same  wood,  but 
usually  one  form  prevails.  These  features  have  considerable 
diagnostic  value.  For  example,  the  perforations  are  simple  in 
Acer,  but  scalariform  in  Betula  and  Cornus;  in  Msculus  and  Tilia 
they  are  mostly  simple,  but  in  Liriodendron  and  Magnolia  scalari- 
form, except  in  Magnolia  acuminata. 

Other  characteristics  of  the  vessels  are  the  markings  on  their 
walls.  In  most  cases  they  are  abundantly  pitted  with  bordered 
pits,  except  in  contact  with  parenchymatous  cells  where  the 
pitting  may  be  either  simple  or  bordered.  (See  Pits.)  It  is  very 
common  for  vessels,  particularly  the  small  ones,  to  be  marked  with 
spirals  on  their  interior  walls  {e.g.,  Acer,  Ilex,  Tilia,  Ostrya,  JZs- 
culus).  In  Liquidambar  only  the  pointed  ends  of  the  vessel  seg- 
ments are  marked  with  spirals. 

The  function  of  vessels  is  to  facilitate  the  ascent  of  water  in 
the  stem.  Vessels  lose  their  protoplasmic  contents  by  the  time 
their  perforations  are  complete  and  become  filled  with  air  and 
water,  or  air  alone.  When  their  activity  as  water-carriers  lessens 
they  frequently  become  plugged  with  outgrowths  from  adjoining 
parenchymatous  cells.  (See  Tyloses.)  In  the  heartwood  of 
certain  species  (e.g.,  Gymnocladus,  Gleditsia,  Guaiacum,  Prosopis) 
they  become  wholly  or  partly  filled  with  gums  or  resins;  in 
others,  with  carbonate  of  lime. 

The  length  of  vessels  is  usually  very  great,  and  doubtless  often 
equals  that  of  the  whole  plant.  In  width  vessels  exhibit  great 
variation  not  only  in  different  species,  but  also  in  different  portions 
of  the  same  growth  ring.  In  some  woods  all  of  the  vessels  are 
small  (e.g.,  Tilia,  JEsculus  [Plate  VI,  Fig.  5],  Populus,  Salix); 
in  others  they  are  mostly  large  (e.g.,  Juglans);  very  often,  as  in 
Quercus  (Plate  II,  Figs.  5,  6),  they  vary  from  large  (0.6  mm.*) 
and  conspicuous  to  very  small  (0.1  mm.). 

Vessels  in  cross  section  are  called  pores,  and  when  this  term 
is  employed  it  will  be  understood  to  apply  to  cross  sections 
exclusively.  Pores  are  usually  readily  distinguishable  from  the 
adjoining  elements  by  their  larger  size,  though  it  is  not  always 

*  One  millimetre  is  equal  to  about  one  twenty-fifth  of  an  inch. 


16  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

possible  to  tell  small  pores  from  cross  sections  of  tracheids.  In 
outline  pores  may  be  round,  elliptical,  or  angular.  The  first 
two  cases  are  the  rule  where  the  vessel  walls  are  thick  enough  to 
resist  the  pressure  of  the  surrounding  elements.  This  is  the  case, 
for  example,  in  the  small  pores  of  the  red  and  live  oaks  (Plate  II, 
Fig.  6),  while  in  the  white  oaks  (Frontispiece;  Plate  II,  Fig.  5) 
the  walls  are  thin  and  the  pores  angular  in  outline.  Sometimes 
pores  are  disposed  in  rings  or  zones  in  the  early  wood  of  the 
growth  ring,  producing  ring-porous  woods  (Plate  III) ;  in  other 
cases  they  are  scattered  singly  or  in  groups  throughout  the 
ring  or  arranged  in  radial  or  tangential  rows,  producing  diffuse- 
porous  woods  (Plate  VI).  (See  Growth  Rings.)  In  any  case 
the  largest  pores  are  almost  invariably  in  the  first  formed  wood 
of  the  season.  The  distribution,  size,  form,  and  arrangement  of 
the  pores  are  characters  of  great  importance  in  classifying  woods. 

References 

Socereder,  H.:  Anatomy  of  the  Dicotyledons,  Vol.  II,  p.  1136. 

Mell,  C.  D.:   History  of  the  Investigations  of  Vessels  in  Wood,  Proc.   Soc. 

Am.  Foresters,  Vol.  VI,  No.  1,  1911,  pp.  78-91. 
DeBary,  A.:  Comparative  Anatomy,  pp.  155-171;   503. 
Mayr,  H.:  Schlich's  Manual  of  Forestry,  Vol.  V,  1908,  pp.  9-10. 
Sanio,  Carl:  Bot.  Zeitung,  Vol.  XXI,  No.  15,  1863,  pp.  121-128. 
Hartig,  R.:  Lehrbuch  der  Anatomie  und  Physiologie  der  Pflanzen,  Berlin, 

1891,  pp.  79-93. 

TRACHEIDS 

Tracheids  are  elongated,  spindle-shaped,  fibre-like  elements, 
determinate  in  length  and  characterized  by  bordered  pits  in 
their  side-walls. 

In  the  wood  of  Gymnosperms  the  tracheid  is  the  dominant 
element,  performing  the  dual  function  of  conducting  water  and 
providing  mechanical  support  for  the  tree.  Bordered  pits  are 
mostly  confined  to  the  radial  walls,  except  in  late  wood,  and  are 
most  abundant  near  the  ends  of  the  tracheids  and  in  one  or  two 
rows  (Fig.  2,  D) .  Seen  in  cross  section,  the  tracheids  are  polygonal 
in  outline,  arranged  in  radial  rows,  and,  near  the  periphery  of 
growth  ring,  with  very  appreciable  increase  in  thickness  of  the 
wall,  reduction  of  the  lumen,  and  tangential  flattening  (Fig.  8; 
Plate  II,  Figs.  1,  2,  4).    In  a  few  species,  particularly  Pseudotsuga, 


ECONOMIC   WOODS   OF   THE   UNITED   STATES 


17 


Taxus,  and  Tumion,  the  tracheids  are  characterized  by  spiral 
thickenings  on  the  inner  wall. 

TABLE   I 

LENGTH   OF   TRACHEIDS   IN   CONIFEROUS   WOODS 


Botanical  Name 


Abies  balsamea 

"      concolor 

"      grandis 

Chamaecyparis  lawsoniana 
"  thyoides  . . 

Larix  occiden talis 

Libocedrus  decurrens .... 
Picea  engelmanni 

"      rubens 

"     sitchensis 

Pinus  echinata 

"      edulis 

"      lambertiana 

"      monticola 

"      murrayana 

"      palustris 

"      ponderosa 

"      resinosa 

"      strobus 

"      taeda 

"      virginiana 

Pseudotsuga  taxif olia 
Sequoia  sempervirens 
"        washingtoniana .  . 

Taxodium  distichum 

Thuya  occidentalis 

"       plicata 

Tsuga  canadensis 

"       heterophylla 


Average      Maximum    Minimum 
mm.  mm.  mm. 


3.10 
4.65 
4.15 
3.60 
2.10 
2.60 
4.00 
5.70 
2.95 
2.85 
5.90 
1.95 
4.45 
4.40 
2.65 
5.55 
3.30 
4.05 
3.55 
3.10 
2.75 
2.70 
7.00 
4.80 
4.70 
2.00 
3.85 
4.00 
3.05 


4.20 
6.00 
5.70 
4.35 
2.80 
3.80 
4.70 
6.95 
3.65 
3.70 
7.20 
2.55 
5.85 
5.45 
3.70 
6.70 
4.00 
4.80 
4.55 
3.90 
3.95 
3.30 
9.25 
5.95 
5.80 
2.40 
4.55 
5.05 
3.65 


2.00 
2.75 
2.90 
2.55 
1.45 
1.75 
3.00 
3.05 
2.50 
2.30 
4.40 
1.50 
2.75 
2.75 
1.80 
3.00 
2.50 
3.20 
3.20 
2.55 
1.75 
1.80 
4.05 
3.45 
3.65 
1.40 
3.15 
2.80 
1.75 


In  certain  conifers,  particularly  Pinus,  specialized  forms  of 
tracheids  of  a  parenchymatous  type  are  found  associated  with 
resin  ducts  and  cysts.  They  resemble  wood-parenchyma  cells  in 
form  and  function,  but  have  bordered  pits  in  their  side  and  end 
walls.  "Resinous  tracheids"  are  ordinary  tracheids  with  deposits 
of  resin  usually  in  the  form  of  thin  transverse  plates. 

The  tracheids  of  broadleaf  woods  (Fig.  2,  E)  are  subordinate 


18  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

elements  often  entirely  wanting.  They  are  much  smaller  and  less 
uniform  in  size  and  shape  than  in  conifers,  and  are  of  most  common 
occurrence  in  the  immediate  vicinity  of  vessels.  Their  ends  are 
often  curved,  especially  when  they  terminate  just  above  or  below 
a  ray.  The  walls  are  usually  comparatively  thin  and  bear  numer- 
ous bordered  pits  very  irregularly  distributed.  Intermediate 
forms  of  tracheids  are  sometimes  found  which  show  distinct 
transition  to  the  vessels  in  the  detailed  structure  of  their  walls 
and  in  the  occasional  presence  of  perforations  at  the  ends  of  the 
cells. 

References 

Penhallow,  D.  P.:  North  American  Gymnosperms,  pp.  33-58. 

DeBary,  A. :    Comparative  Anatomy,  pp.  164-165. 

Thompson,  W.  P. :    On  the  Origin  of  Ray  Tracheids  in  the  Coniferse,  Bot. 

Gazette,  Vol.  L,  1910,  pp.  101-116. 
Kxy,  L.:    Ein  Beitrag  zur  Entwickelungsgeschichte  der  "Tracheiden,"  Ber. 

d.  deutschen  Bot.  GeseUschaft,  Vol.  IV,  1886,  pp.  267-276. 
Sanio,  Carl:    Botanische  Zeitung,  Vol.  XXI,  No.  14,  1863,  pp.  113-118. 

WOOD    FIBRES 

Typical  wood  fibres  (Fig.  2,  A,  B)  are  slender,  spindle-shaped, 
sharp-pointed  cells  with  thick  walls  and  narrow  cavities.  They 
are  further  characterized  by  usually  oblique  and  slit-like  simple 
pits,  or  less  frequently  by  small,  indistinctly  bordered  pits.  Wood 
fibres  are  not  found  in  Gymnosperms,  but  are  nearly  always 
present  in  the  wood  of  Dicotyledons. 

Wood  fibres  are  of  two  types,  septate  and  ordinary  {non- 
septate).  The  septate  forms  are  divided  by  cross-partitions 
formed  after  thickening  of  the  walls  has  begun.  They  are  of 
limited  occurrence  and  of  relatively  small  importance.  They 
are  characteristic  of  Swietenia  mahagoni  and  serve  as  one  means 
of  distinguishing  the  wood  from  that  of  certain  others  closely 
resembling  it. 

The  ordinary  forms  are  very  common  and  are  the  principal 
source  of  strength,  hardness,  and  toughness  of  broadleaf  woods. 
While  their  function  is  largely  mechanical,  it  is  probable  that 
they,  especially  those  with  bordered  pits,  play  some  part,  as  yet 
undetermined,  in  water  transportation. 

Wood  fibres  exhibit  transitional  forms  from  the  typical  to 
tracheids  on  one  hand,  and  to  wood-parenchyma  strands  on  the 


ECONOMIC    WOODS    OP   THE    UNITED    STATES 


19 


other.  In  structure  and  arrangement  they  exhibit  variations  of 
considerable  taxonomic  value.  For  example,  in  Ilex  the  fibres 
are  rather  thin-walled  and  marked  with  spirals  and  bordered  pits, 
and  closely  resembling  tracheids  except  for  their  greater  size. 
In  Liquidambar  (Plate  VI,  Fig.  1)  the  fibres  are  mostly  square  in 
cross  section    and    in  rather    definite    radial    arrangement.      In 


*  B 

Fig.  2. — Typical  Wood  Cells.  A,  Wood  fibre  with  very  narrow  lumen;  B, 
wood  fibre  with  larger  lumen  and  showing  oblique,  slit-like  simple  pits  (s.  p.) ; 
C,  end  of  wood  fibre  showing  saw  edge;  C,  end  of  wood  fibre  showing  forked 
.structure;  D,  ends  of  two  tracheids  from  Pinus  showing  numerous  bordered  pita 
(b.  p.) ;  E,  Tracheid  from  Quercus;  F,  wood-parenchyma  strand,  showing  individual 
cells  and  simple  pits  (s.  p.) ;  G,  chambered  wood-parenchyma  strand  from  Juglans, 
showing  crystals  of  calcium  oxalate;  H,  conjugate  parenchyma  cells;  K,  portion 
of  a  vessel  segment  showing  simple  perforation  (p) ;  L,  portion  of  a  vessel  segment 
showing  scalariform  perforation  (Sc.  p.).     Greatly  enlarged. 

Robinia  (Plate  III,  Fig.  3)  and  Toxylon  they  are  in  rather  large, 
compact  masses  in  the  late  wood,  separated  by  groups  or  bands  of 
pores  and  parenchyma.  In  any  wood  in  which  they  occur  they  are 
most  abundant  in  the  median  portion  of  the  growth  ring,  and 
material  decrease  in  the  width  of  a  ring  is  usually  at  their  expense. 
The  ends  of  most  wood  fibres  are  smooth  and  uniformly 


20 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


tapering,  but  sometimes  they  are  flattened,  or  forked,  or  with  a 
saw  edge  (Fig.  2,  C,  C),  adding  to  the  toughness  of  the  wood. 
Fibres  usually  run  parallel  to  one  another,  but  in  some  woods 
they  exhibit  a  decided  interweaving  which  produces  an  irregularly 
grained  wood  very  difficult  to  split. 

TABLE  II 
Length  of  Wood  Fibres  in  Dicotyledonous  Woods 


Botanical  Name 


Acer  rubrum 

Betula  nigra 

Castanea  dentata 

Celtis  occidentalis 

Fagus  americana 

Hicoria  alba 

Ilex  opaca 

Juglans  nigra 

Liquidambar  styraciflua 
Liriodendron  tulipifera . 
Magnolia  acuminata .  .  . 

Nyssa  sylvatica 

Platanus  occidentalis. . . 
Populus  deltoides 

"        grandidentata . 

"        heterophylla. . . 

"        trichocarpa 

Quercus  alba 

"        coccinea 

"        michauxii 

"        rubra 

"        virginiana 

Salix  nigra 

Tilia  americana 

Ulmus  americana 


Average 

Maximum 

mm. 

mm. 

.75 

1.00 

1.80 

2.20 

1.15 

1.45 

1.25 

1.70 

1.20 

1.70 

1.35 

1.70 

1.45 

2.00 

1.10 

1.65 

1.60 

2.00 

1.90 

2.50 

1.75 

2.30 

1.70 

2.35 

1.90 

2.30 

1.40 

2.20 

1.00 

1.35 

1.35 

1.80 

1.15 

1.90 

1.25 

1.50 

1.50 

2.10 

1.55 

1.80 

1.20 

1.45 

1.40 

1.80 

.85 

.95 

1.15 

1.45 

1.50 

1.90 

.50 

1.50 

.80 

1.05 

.75 

.90 

1.15 

.65 

1.25 

1.40 

1.00 

1.05 

1.30 

.50 

.65 

1.00 

.50 

1.00 

1.00 

1.10 

.70 

.85 

.45 

.85 

1.15 


References 
DeBary,  A.:    Comparative  Anatomy,  pp.  481-483. 
Solereder,  H.:    Anatomy  of  the  Dicotyledons,  Vol.  II,  pp.  1141-1143. 
Gregory,  E.  L.:   Pores  of  the  Libriform  Tissue,  Bull    Torrey  Bot.  Club,. 

Vol.  XIII,  1886,  pp.  197-204;  233-244. 
Anonymous:    Length  of  Wood  Fibers  in  Broadleaf  Woods,  Sc.  American 

Sup.,  Sept.  30,  1911,  p.  211. 
Sanio,  Carl:   Bot.  Zeitung,  Vol.  XXI,  No.  13,  1863,  pp.  89-111. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  21 


WOOD    PARENCHYMA 

Parenchyma  occurs  in  the  secondary  xylem  of  all  woody 
plants,  and,  with  few  exceptions,  is  disposed  in  two  systems: 
(1)  the  vertical,  composed  of  more  or  less  scattered  rows  of  cells 
forming  the  wood  parenchyma;  and  (2)  the  horizontal,  made  up  of 
plates  of  cells  extending  radially  and  at  right  angles  to  the  axis  — 
the  medullary  rays  or  pith  rays.  Its  chief  function  is  the  distribu- 
tion and  storage  of  elaborated  food  materials. 

Typical  wood-parenchyma  strands  (Fig.  2,  F;  Plate  IV,  Figs. 
5,  6)  of  Dicotyledons  resemble  septate  wood  fibres,  but  have  (1) 
thinner  walls,  (2)  simple,  rounded  or  lenticular  pits  instead  of 
oblique,  slit-like  simple  or  bordered  pits,  and  (3)  cross  walls  equal 
in  thickness  to  the  lateral  walls.  The  individual  cells  of  a  wood- 
parenchyma  strand  are  mostly  short  and  prismatic,  pitted  with 
simple  pits  and  (with  the  exception  of  the  terminal  ones,  which 
are  pointed)  with  transverse  or  oblique  end  walls.  Between 
wood  fibres  and  wood-parenchyma  strands  are  intermediate  forms 
without  septa  —  substitute  fibres  or  intermediate  wood  fibres. 

Where  wood  parenchyma  borders  on  large  vessels  it  is  usually 
much  flattened  as  a  result  of  the  pressure  of  the  expanding  vessel 
segments.  In  such  locations  also  are  sometimes  special  forms 
termed  conjugate  cells  because  of  flatly  tubular  processes  extending 
from  one  to  another  slightly  distant,  thus  uniting  them  (Fig.  2,  H). 

There  are  special  forms  of  wood  parenchyma  in  which  the 
individual  cells  are  divided  by  cross  walls  into  small  chambers 
of  approximately  even  size  which  contain  solitary  crystals,  usually 
of  calcium  oxalate  (Fig.  2,  G;  Plate  IV,  Fig.  6).  Such  crystals 
are  only  slightly  soluble  even  in  the  strongest  acids,  and  are  very 
plainly  visible  under  high  magnification  in  both  cross  and  longi- 
tudinal sections.  Crystals  occur  in  all  species  of  Quercus,  though 
they  are  commonly  more  abundant  in  the  five  oaks  than  in  decid- 
uous species.  In  Juglans  (Plate  IV,  Fig.  6),  Hicoria  (Plate  IV, 
Fig.  3),  and  Diospyros,  crystals  are  often  quite  conspicuous. 
Calcium-oxalate  crystals  are  also  common  in  ray-parenchyma 
cells. 

The  distribution  and  arrangement  of  wood-parenchyma  strands 
in  different  species  are  subject  to  considerable  variation.  As  seen 
on  cross  sections  of  woody  Dicotyledons  the  cells  may  be  (a) 
scattered  irregularly  throughout  the  growth  ring  (Plate  V,  Figs. 
3,  5),   (6)  arranged  in  tangential  lines  or  bands  (Frontispiece, 


22  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

Plate  IV,  Figs.  1,  2),  (c)  terminal,  i.e.,  comprising  the  outer  limit 
of  the  growth  ring  (Plate  III,  Fig.  6;  Plate  V,  Fig.  2;  Plate  VI, 
Fig.  2),  (d)  surrounding  pores  (Plate  III,  Figs.  3,  5),  (e)  ar- 
ranged in  radial  rows.  These  features  are  quite  important  in 
classifying  woods.  For  example,  in  Fraxinus  americana  the  pores 
in  the  late  wood  are  usually  joined  tangentially  by  narrow  bands 
of  wood  parenchyma,  while  in  F.  nigra  (Plate  V,  Fig.  2)  the  pores 
are  rarely  so  united.  In  Hicoria  (Plate  IV,  Fig.  1)  wood  paren- 
chyma is  in  numerous,  fine,  concentric  lines  as  distinct  as  the 
rays,  while  in  Diospyros  (Plate  IV,  Fig.  2)  the  lines  are  finer  than 
the  rays  and  very  indistinct.  In  Tilia  wood  parenchyma  is  in 
tangential  lines,  but  is  not  so  disposed  in  Liriodendron,  Magnolia, 
and  Msculus.  In  Liriodendron  (Plate  VI,  Fig.  2)  and  Magnolia 
the  outer  limit  of  the  growth  ring  consists  of  2-4  rows  of  tan- 
gentially flattened  wood-parenchyma  cells  with  very  thick,  copi- 
ously pitted  radial  walls. 

Wood  parenchyma  is  present  in  the  wood  of  all  Gymnosperms 
except  the  Taxacece.  The  cells  are  invariably  associated  with 
resin  formation  and  are  usually  referred  to  as  resin  cells  or  epithelial 
cells,  according  as  they  are  more  or  less  scattered  or  surrounding 
resin  ducts. 

Resin  cells  are  usually  cylindrical  or  prismatic,  thin-walled, 
with  transverse  terminations  more  or  less  strongly  marked  with 
simple  pits.  The  pits  in  the  side  walls  are  often  few  and  invariably 
simple.  Resin  cells  can  usually  be  distinguished  on  cross  sections 
under  the  microscope  by  their  thin  walls,  simple  pits,  or  better 
by  the  deep  color  of  their  contents.  If  the  section  passes  near 
enough  to  an  end  wall  the  simple  pits  therein  give  the  appearance 
of  a  sieve  plate  (Fig.  10).  While  in  most  cases  resin  cells  are 
invisible  without  the  microscope,  and  often  not  readily  found  with 
it,  yet  in  Juniperus,  Taxodium,  and  Sequoia  they  are  usually 
conspicuous,  not  infrequently  giving  rise  in  the  first  two  species 
to  wavy  tangential  lines  in  the  growth  ring,  visible  to  the  unaided 
eye. 

The  distribution  of  the  resin  cells  is  variable.  In  some  cases 
(e.g.,  Thuya)  they  are  scattering;  in  others  (e.g.,  Taxodium  [Plate 
II,  Fig.  1],  Juniperus  [Plate  II,  Figs.  3,  4],  Libocedrus)  they  are 
disposed  in  well-defined  zones  concentric  with  the  growth  ring, 
being  most  abundant  as  a  rule  in  the  transition  zone  between 
early  and  late  wood.  In  still  other  cases  (e.g.,  Tsuga)  there  is 
often  a  tendency  of  some  of  the  resin  cells  to  aggregation,  and  in 


ECONOMIC   WOODS   OF   THE    UNITED    STATES  23 

some  cases  the  formation  of  imperfect  resin  ducts  or  resin  cysts 
(Fig.  10).     (See  Resin  Ducts.) 

In  Pinus  (Fig.  8)  wood  parenchyma  is  found  only  in  association 
with  resin  ducts,  isolated  resin  cells  being  absent;  while  in  Larix 
and  Pseudotsuga  resin  cells  are  occasionally  found  on  the  extreme 
outer  face  of  the  late  wood.  In  Abies  resin  cells  are  remote  and 
inconspicuous;  in  Thuya  plicata  they  are  present,  though  often 
zonate  in  widely  separated  growth  rings,  thus  often  apparently 
absent.  In  Sequoia  (particularly  S.  sempervirens)  the  resin  cells 
are  partially  filled  with  dark  resin  masses  which  appear  on  longi- 
tudinal surface  as  fine  dotted  lines,  or  under  lens  as  rows  of  black 
or  amber  beads. 

References 

DeBary,  A.:    Comparative  Anatomy,  pp.  4S5-4S6. 
Penhallow,  D.  P.:    North  American  Gymnosperms,  pp.  109-122. 
Boulger,  G.  S.:   Wood,  pp.  28-29. 

Sanio,  Carl:   Bot.  Zeitung,  Vol.  XXI,  No.  12,  pp.  93-98. 
Kny,  L.:    Ueber  Krystallbildung  beim  Kalkoxolat,  Berichte  der  deutschen 
Bot.  Gesellschaft,  Vol.  V,  1887,  pp.  387-395. 

RAYS 

Medullary  or  pith  rays,  for  brevity  termed  simply  rays, 
appear  on  the  cross  section  of  a  stem  as  radial  lines  crossing  the 
growth  rings  at  right  angles  and  extending  into  the  bark  (Fig.  1). 
A  few  of  them  originate  at  the  pith  and  are  commonly  known  as 
primary  rays.  Successively,  as  the  stem  increases  in  size,  addi- 
tional or  secondary  rays  arise  between  those  already  formed. 
A  ray  may  arise  in  the  cambium  layer  at  any  point,  and  once  formed 
its  growth  is  continuous.* 

Under  the  microscope  the  line  formed  by  the  ray  becomes  a 
radial  series  of  mostly  elongated  cells  usually  with  transverse 
end  walls  (Plates  II-IV).  Viewed  radially  a  ray  appears  as  a 
muriform  structure  composed  of  from  one  to  many  tiers  of  brick- 
shaped  cells  (Plate  IV,  Figs.  5,  6).  In  tangential  section  the  ends 
of  the  rays  are  visible,  showing  to  advantage  their  height,  shape, 

*  When  on  cross  or  radial  sections  a  ray  appears  to  be  discontinuous,  it  is 
probable  that  it  has  merely  been  missed  by  the  plane  of  section.  This  empha- 
sizes the  importance  of  making  cross  sections  exactly  at  right  angles  to  the 
axis  of  growth,  and  radial  sections  as  nearly  as  possible  parallel  with  the  rays. 


jlvvmh  aimjohj 


24 


ECONOMIC    WOODS    OF    THE    UNITED    STATES 


width,  and  distribution,  and  also  the  outline  in  cross  section  of 
the  component  cells  (Plate  III,  Fig.  1;  Plate  IV,  Figs,  3,  4;  Plate 
VI,  Figs.  3,  4,  6). 

Ray  cells  are  usually  elongated  in  the  radial  direction.  This  is 
normally  the  case  in  Gymnosperms  and  usually  so  in  the  woody 
Dicotyledons.  Not  infrequently  in  the  latter,  however,  part  or 
all  of  the  cells  are  upright,  i.e.,  with  their  greatest  diameter  vertical, 
or  are  square.  The  marginal  cells  are  sometimes  upright  and  the 
interior  cells  radially  elongated  or  procumbent  (Fig.  3).  The  upright 
cells  are  often  very  irregular,  especially  the  outermost  marginal 
rows;  sometimes  they  are  nearly  square;  again  they  are  in  pali- 
sade arrangement.     When  these  upright  or  square  cells  are  in 


Fig.  3. — Radial  sections  of  heterogeneous  rays.  A,  Sassafras  sassafras  (sassa- 
fras);  B,  Nyssa  sylvatica  (black  gum);  C,  AZsculus  octandra  (buckeye),  showing 
large  pits  (I.  p.)  in  upright  cells  (up.  a),  where  they  adjoin  vessels;  and  small  pita 
(s.  p.),  in  procumbent  cells  (pr.  c).  No  pits  are  shown  in  A  and  B.  Magnified 
about  150  diameters. 


contact  with  large  vessels  the  separating  walls  are  characteristically 
marked  with  very  large  pits  whose  polygonal  or  oval  outlines 
present  the  appearance  of  lattice  work  (Fig.  3,  C).  The  lateral 
walls  of  similarly  located  procumbent  cells  usually  contain  few 
small  pits.  Moreover,  in  proximity  to  large  vessels  the  walls 
between  all  ray  cells  are  usually  thicker  and  much  more  abun- 
dantly pitted  than  elsewhere.  Upright  cells  are  not  always  easy 
to  distinguish  from  the  cells  of  wood-parenchyma  fibres,  especially 
where  they  cross  the  latter,  on  account  of  the  similar  direction  of 
their  longitudinal  diameters. 


ECONOMIC   WOODS   OF   THE   UNITED    STATES 


25 


Rays  consisting  wholly  of  procumbent  cells  may  be  said  to  be 
homogeneous;  those  which  contain  both  upright  and  procumbent 
cells,  heterogeneous  (Fig.  3) .  Heterogeneous  rays  are  characteristic 
of  many  dicotyledonous  woods,  and  are  features  of  importance  in 
classification.  For  example,  Celtis  has  heterogeneous  rays,  while 
those  of  Ulmus  are  homogeneous.  The  same  distinction  obtains 
between  Salix  and  Populus,  Sassafras  and  Fraxinus.  The  rays  of 
Sassafras  are  peculiar  in  having  a  few  of  the  marginal  cells  abnor- 
mally large  and  rounded  or  ovate  (Fig.  3,  A). 

The  rays  in  the  wood  of  Gymnosperms  are  for  the  most  part 
one  cell  wide,  i.e.,  uniseriate,  and  from  1  to  20  cells  high.    It  is  not 


r.tr. 


r.p._ 


r.tr. 


Fig.  4. — Radial  section  of  ray  of  Pinus  strobus  (white  pine) ;  showing  the 
smooth  upper  and  lower  walls  of  the  ray  tracheids  (r.  ir.),  and  the  presence  in  the 
lateral  walls  of  the  ray-parenchyma  cells  (r.  p.)  of  large  simple  pits  (s.  p.),  com- 
municating with  the  wood  tracheids  (w.  tr.)  adjacent;  b.  p.,  bordered  pits.  Magni- 
fied about  250  diameters. 


uncommon  to  find  biseriate  rays,  and  those  which  contain  resin 
ducts  (Pinus,  Picea,  Larix,  Pseudotsuga)  are  multiseriate.  The 
latter,  because  of  their  shape  as  seen  on  tangential  section,  are 
called  fusiform  rays  (Fig.  9) . 

In  woody  Dicotyledons  there  is  more  variation  in  the  rays. 
In  some  instances  {e.g.,  Msculus  [Plate  VI,  Fig.  6],  Salix,  Populus) 
low  uniseriate  rays  only  are  present.  At  the  other  extreme  is 
Quercus  (Plate  III,  Fig.  1),  where  the  largest  rays  are  from  25  to 


26 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


75  cells  wide  and  several  hundred  high.  These  large  rays  give  rise 
to  the  handsome  figure  of  quarter-sawed  {i.e.,  radially  cut)  oak 
lumber.  Besides  the  large  rays  in  Quercus  there  are  numerous 
intermediate  ones,  mostly  uniseriate  and  1-20  cells  high  (Plate 
III,  Fig.  1).  In  Platanus  the  rays  are  uniformly  broad  (10-15 
cells),  while  in  Fagus  only  a  portion  of  the  rays  are  broad  (15-25 
cells),  the  intermediate  ones  being  uniseriate.  In  some  of  the 
evergreen  oaks,  Carpinus  and  species  of  Alnus  (Plate  V,  Figs.  3,  4), 
the  large  rays  appear  to  be  composed  of  numerous  small  ones 


r.tr 


Fig.  5. — Radial  section  of  a  ray  of  Pinus  edulis  (piflon  pine),  showing  the 
smooth  upper  and  lower  walls  of  the  ray  tracheids  (r.  tr.),  and  the  presence  in  the 
lateral  walls  of  the  ray-parenchyma  cells  (r.  p.)  of  small  semi-bordered  pits  (s.  b.  p.), 
communicating  with  the  wood  tracheids  (w.  tr.)  adjacent;  s.  p.,  simple  pit;  b.  p., 
bordered  pit.     Magnified  about  250  diameters. 

separated  by  wood  fibres.  Such  rays  are  termed  aggregate  or 
compound  rays;  sometimes  also  false  rays.  Every  ray,  regardless 
of  its  width  at  the  middle,  tapers  to  an  edge  so  that  the  upper 
and  lower  margins  are  a  single  cell  wide.* 

The  comparative  distinctness  which  rays  on  cross  section 
present  to  the  unaided  eye  is  important  in  separating  certain 
woods  which    bear    superficial  resemblance.     For  instance,  the 


For  this  reason  cross  sections  often  do  not  afford  a  correct  idea  of  ray 


width. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


27 


rays  in  Sassafras  are  much  more  distinct  than  in  Fraxinus;  like- 
wise in  Celtis  and  Ulmus,  Tilia  and  JZsculus,  Acer  and  Betula. 
In  white  oaks  the  height  of  the  large  rays  averages  considerably 
greater  than  in  the  red  or  live  oaks. 

In  dicotyledonous  species  the  rays  are  composed  wholly  of 
parenchyma.  In  certain  Gymnosperms  (Pinus,  Larix,  Picea, 
Pseudotsuga,  Tsuga,  and  occasionally  in  others)  ray  tracheids  are 
present  (Figs.  4-7).  They  are  usually  marginal,  but  often  inter- 
spersed and  sometimes  they  compose  entire  rays,  particularly 


Fig.  6. — Radial  section  of  a  ray  of  Pinus  resinosa  (red  or  Norway  pine), 
showing  the  dentations  (d)  or  reticulations  on  the  upper  and  lower  walls  of  the  ray 
tracheids  (r.  tr.),  and  the  presence  in  the  lateral  walls  of  the  ray-parenchyma  cells 
(r.  p.),  of  large  simple  pits  (s.  p.)  communicating  with  the  wood  tracheids  {w.  tr.) 
adjacent;   b.  p.,  bordered  pit.     Magnified  about  250  diameters. 


low  ones.  They  can  be  distinguished  from  the  ray-parenchyma 
cells  by  the  presence  of  bordered  pits  in  the  lateral  and  especially 
the  end  walls.  They  are  often  irregular  in  outline  and  are  devoid 
of  visible  contents.  They  have  their  counterparts  in  the  paren- 
chymatous tracheids  surrounding  the  epithelial  cells  of  resin  cysts 
and  ducts.  In  the  young  root,  and  sometimes  in  the  young  stem 
as  well,  special  upright  or  oblique  forms  occur  which  may  be 
considered  as  transitional  from  wood  tracheids  to  ray  tracheids. 

The  character  of  the  upper  and  lower  walls  of  the  ray  tracheids, 
whether  smooth,  as  in  soft  pines,  or  dentate  or  reticulate,  as  in 


28 


ECONOMIC    WOODS    OF   THE    UNITED    STATES 


pitch  pines,  affords  a  constant  diagnostic  feature  of  much  im- 
portance in  separating  the  two  great  groups  of  Pinus  (Figs.  4-7). 
Ray-parenchyma  cells  in  general  communicate  with  each  other, 
with  the  ray  tracheids,  and  with  the  adjacent  wood  elements  by 
means  of  pits  always  simple  in  the  wall  of  the  parenchyma  cell, 


r.tr 


Ir^f- 


Fig.  7. — Radial  section  of  a  ray  of  Pinus  palustris  (longleaf  pine),  showing  the 
dentations  (d)  or  reticulations  on  the  upper  and  lower  walls  of  the  ray  tracheids 
(r.  tr.J,  and  the  presence  in  the  lateral  walls  of  the  ray-parenchyma  cells  (r.  p.)  of 
small  simple  pits  (s.  p.),  communicating  with  the  wood  tracheids  (w.  tr.)  adjacent; 
b.  p.,  bordered  pit.     Magnified  about  250  diameters. 

but  commonly  more  or  less  bordered  in  the  other.  Often  certain 
cells  of  a  ray  have  thicker  vvalls  and  more  numerous  pits  than  the 
others. 

References 
Penhallow,  D.  P.:    North  American  Gymnosperms,  pp.  78-108. 
Bailey,  I.  W.:    On  the  Origin  of  the  Broad  Ray  in  Quercus,  Bot.  Gaz.,  Vol. 

XLIX,  No.  3,  March  1910,  pp.  161-167. 
:    Notes  on  the  Wood  Structure  of  the  Betulacese  and  Fagaceae, 

Forestry  Quarterly,  Vol.  VIII,  No.  2,  1910,  pp.  178-185. 
:    The    Relation    of    Leaf -Trace    to   Compound    Rays   in    Lower 

Dicotyledons,  Annals  of    Botany,  Vol.  XXV,  No.  97,  January  1911, 

pp.  225-241. 
Groom,  Percy:    The  Evolution  of  the  Annual  Ring  and  Medullary  Rays  of 

Quercus,  Annals  of  Botany,  Vol.  XXV,  No.  100,  October  1911,  pp. 

983-1004. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES  29 

Thompson,  W.  P. :    On  the  Origin  of  the  Multiseriate  Ray  of  the  Dicotyledons, 

Annals  of  Botany,  Vol.  XXV,  No.  100,  October  1911,  pp.  1005-1014. 
:  The  Origin  of  Ray  Tracheids  in  the  Coniferse,  Bot.  Gaz.,  Vol.  L, 

No.  2,  1910,  pp.  101-116. 
Kny,  L.:    Beitrag  zur  Kenntnis  der  Markstrahlen  dicotyler  Holzgewachse, 

Berichte  d.  deutschen  Bot.  Gesellschaft,  Vol.  VIII,  Berlin,  1890,  pp. 

176-188. 
Essner,  Benno:    Ueber  den  diagnostischen  Werth  der  Anzahl  und  Hohe  der 

Markstrahlen  bei  den  Coniferen,  Halle  A.  S.,   1882.     See  also  Bot. 

Centralblatt,  Vol.  XII,  No.  12,  1882,  pp.  407-408. 
Zijlstra,   K. :    Die  Gestalt  der  Markstrahlen  in  sekundaren    Holze,   Rec. 

Trav.  bot.  neerl.,  V,  1908,  pp.  17-20. 

RESIN    DUCTS 

Resin  ducts  are  long,  narrow,  intercellular  channels  surrounded 
by  parenchyma  cells  and  rilled  with  resin  (Fig.  8).  Unlike  vessels, 
they  have  no  walls  of  their  own,  but  are  limited  by  a  layer  of  cells 
called  epithelium.  The  epithelial  cells  are  thin-walled  in  Pinus 
and  mostly  thick-walled  in  Larix,  Picea,  and  Pseudotsuga.  When 
thick-walled  the  cells  are  rounded  and  show  clearly  in  cross  sec- 
tion, while  those  with  thin  walls  are  compressed  and  very  likely 
to  be  torn  in  sectioning. 

Resin  cysts  are  very  short,  duct-like,  intercellular  spaces  very 
common  in  Sequoia,  Tsuga,  and  Abies.  Not  infrequently  they 
are  in  longitudinal  series,  but  differ  from  a  true  duct  in  having 
numerous  constrictions. 

Resin  ducts  are  largest  and  most  abundant  in  Pinus,  where 
they  are  fairly  well  distribut  :d  throughout  the  growth  ring,  though 
usually  more  numerous  in  the  transition  zone  between  early  and 
late  wood.  They  are  comparatively  large  in  most  species,  averag- 
ing about  0.25  mm.,  and  are  readily  visible  to  the  unaided  eye. 
On  longitudinal  surface  they  appear  as  long,  delicate  lines  like 
pin  scratches,  filled  with  resin.  In  Larix,  Picea,  and  Pseudotsuga 
the  ducts  are  smaller,  sometimes  invisible  without  lens,  fewer  in 
number,  and  irregularly  distributed,  often  more  or  less  grouped. 

In  addition  to  the  ducts  extending  in  a  vertical  direction,  there 
are  horizontal  ducts  in  the  fusiform  rays  (Fig.  9) .  The  two  series 
are  united  at  infrequent  intervals. 

Resin  ducts  very  commonly  develop  as  a  result  of  injury, 
not  only  in  genera  in  which  they  occur  normally,  but  also  in  others 


30 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


(e.g.,  Tsuga,  Abies,  Sequoia)  where  normally  absent.  The  formation 
of  these  traumatic  resin  ducts,  as  they  are  called,  following  wound- 
ing by  chipping  of  the  outer  layers  of  the  sapwood  of  Pinus 
palustris,  is  the  source  of  most  of  our  turpentine  and  other  naval 
stores.    Traumatic  ducts  can  be  distinguished  from  normal  ones 


l.w. 


Fig.  8. — Cross  section  through  a  portion  of  two  growth  rings  of  Pinus  ponderosa 
(western  yellow  pine);  r.  d.,  resin  duct;  e.,  epithelial  cells;  r.,  ray;  e.  w.,  early 
wood;   I.  w.,  late  wood;   b.  p.,  bordered  pit.     Magnified  about  200  diameters. 


by  their  peculiar  localization,  usually,  as  seen  on  cross  section, 
forming  one  or  more  compact  rows  concentric  with  the  growth 
ring  (Fig.  10). 

Gum  ducts  occur  sporadically  in  the  woods  of  certain  indigenous 
Dicotyledons,  viz.,  Liquiolambar,  Swietenia  and  Prunus. 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  31 

In  Leitneria  floridana  numerous  resin  ducts  are  found  at  the 
margin  of  the  pith,  but  are  not  in  the  wood.  The  epithelial 
cells  are  thick-walled  and  in  a  single  layer. 
Resin  ducts  are  features  of  great  system- 
atic importance.  Their  presence  in  Pinus, 
Picea,  Larix,  and  Pseudotsuga  serves  as  an  ade- 
quate basis  for  separating  the  woods  of  these 
four  genera  from  other  Gymnosperms.  Their 
relative  size,  distribution,  and  occurrence,  and 
the  character  of  the  epithelium,  whether  thick 
or  thin-walled,  are  features  made  use  of  in 
specific  diagnoses. 


References 

Penhallow,  D.  P.:  North  American  Gymnosperms, 
pp.  109-153. 

Kirsch,  Simon  :  The  Origin  and  Development  of  Resin 
Canals  in  the  Coniferse  with  Special  Reference 
to  the  Development  of  Tyloses  and  their  Co- 
relation  with  the  Thylosal  Strands  of  the  Pteri- 
dophytes,  Proc.  Royal  Soc.  of  Canada,  1911. 

Foxworthy,  Fred  W.:  Philippine  Dipterocarpacese. 
Phil.  Journal  of  Science,  C.  Botany,  Vol.  VI, 
No.  4,  Sept.  1911,  pp.  231-287. 

Solereder,  H. :  Anatomy  of  the  Dicotyledons,  Vol. 
II,  pp.  1101-1102. 

Tschirch,  A.:  Die  Harze  und  die  Harzbehalter,  Vol. 
II. 


n 


\r.t. 


All  wood  elements  when  first  formed  are 
limited  by  a  very  thin  cellulose  membrane, 
the  primary  wall.  Subsequent  development 
involves  an  internal  thickening  which  is  com- 
posed very  largely  of  lignin,  the  secondary  wall. 
This  thickening  may  proceed  uniformly,  or,  as 
is  usually  the  case,  small  gaps,  called  pits, 
occur.  A  pit  is  merely  an  unthickened 
portion  of  the  cell  wall.  Pits  are  of  two 
principal  types,  simple  and  bordered  (Fig.  11). 


Fig.  9. — Tangen- 
tial section  of  a  fusi- 
form ray  from  Pinus 
ponderosa  (western 
yellow  pine);  r.  d., 
horizontal  resin 

duct;  e.,  epithelial 
cells;  r.  t.,  ray  tra- 
cheids;  the  remain- 
der of  the  cells  are 
ray-parenchyma 
cells.  Magnified 

about  200  diameters. 


32 


ECONOMIC    WOODS   OF   THE    UNITED    STATES 


Intermediate   forms    exist    whose   reference  to  either   group  is 
.  arbitrary. 

A  simple  pit  is  one  in  which  the  thickening  about  a  spot  on 
the  primary  wall  forms  a  canal  which  is  equally  wide  throughout 
its  length,  or  narrowing  outward  (Fig.  11,  H).  The  length  of  the 
canal  is  determined  by  the  thickness  of  the  secondary  wall.  When 
simple  pits  occur  in  very  thick-walled  cells,  there  is  often  a  tend- 
ency to  a  slight  funnel-formed  enlargement  of  the  canal  toward 


cocoon 


Fig.  10. — Cross  section  of  a  wound  area  in  Tsuga  canadensis  (eastern  hemlock) 
showing  five  traumatic  resin  ducts  (tr.  r.  d.),  in  tangential  row.  Note  thick-walled 
epithelial  cells  (e),  and  occasional  resin  cells  (r.  c),  showing  sieve-like  end  walls. 
Magnified  about  150  diameters. 


the  primary  wall.  Often  the  canal  widens  sufficiently  to  present 
the  appearance  of  a  narrow  border  (Fig.  11,  G).  Seen  in  profile, 
as  in  section,  the  pit  canal  of  such  a  pit  is  narrow  at  the  end 
toward  the  centre  of  the  cell,  but  widens  gradually  outward. 

A  bordered  pit  is  one  in  which  the  canal  widens  suddenly, 
that  is,  with  a  distinct  angle,  toward  the  primary  wall  (Fig.  11,  A). 
In  surface  view  a  bordered  pit  appears  as  a  bright  spot  or  slit 
within  a  circle  or  ellipse  (Fig.  11,  B).  This  outer  circle  marks 
the  limit  of  the  unthickened  area;  the  bright  spot  is  the  inner 
opening  or  aperture  of  the  canal;  the  zone  between  the  two  is 
called  the  border. 

Pits,  especially  bordered  ones,  usually  are  paired  on  opposite 
sides  of  the  primary-cell  walls.  Pits  between  vascular  elements 
are  invariably  bordered;  between  parenchymatous  elements, 
invariably  simple;  between  vascular  and  parenchymatous,  they 
may  be  simple,  but  more  frequently  are  semi-bordered,  that  is, 


ECONOMIC    WOODS    OF    THE    UNITED    STATES 


33 


bordered  in  the  vessel  or  tracheid,  and  simple  in  the  adjacent 
parenchyma  cells  (Fig.  11,  F).  Pits  in  typical  wood  fibres  are 
simple  and  slit-like,  and  usually  in  oblique  position  (Figs.  11,  K; 
2,  B).  In  many  cases,  however,  where  the  fibres  resemble  tracheids 
their  pits  are  more  or  less  bordered.  The  fibres  of  the  bast  have 
only  simple  pits. 

The  shape  of  the  border  is  commonly  circular,  but  may  be 
•oval,  lenticular,  oblong,  or,  in  the  case  of  dense  aggregation,  polyg- 
onal.   Scalariform  markings  found  on  the  vessel  walls  in  certain 


Fig.  11. — Schematic  representation  of  pits,  greatly  enlarged.  A,  section  of 
"bordered  pit  showing  cell  walls  (c.  w.),  primary  cell  wall  (p.  c.  w.),  pit  canal  (c), 
torus  (J) ;  A',  the  same  with  torus  (0  shoved  to  one  side  and  lying  lid-like  against 
the  aperture  of  the  pit  canal;  B,  surface  view  of  bordered  pit  shown  in  A  or  A', 
showing  aperture  (a)  and  border  (6) ;  C,  surface  view  of  bordered  pit  with  lentic- 
ular aperture  (a) ,  the  crossed  appearance  being  due  to  the  fact  that  the  apertures 
on  opposite  sides  of  the  pit  are  shown;  D,  surface  view  of  a  bordered  pit  with 
slit-like  aperture  (a) ,  common  in  thick-walled  tracheids  of  late  wood  in  gymnosper- 
mous  woods;  E,  surface  view  of  scalariform  bordered  pit  with  narrow,  elongated 
aperture  (a)  and  border  (b) ;  F,  section  of  a  semi-bordered  pit  showing  border  on 
one  side  only;  G,  simple  pit  with  funnel-formed  canal  and  appearing  slightly 
bordered  in  surface  view;  H,  ordinary  simple  pit  with  canal  (c)  uniform  or  narrow- 
ing outward  (i.e.,  toward  primary  cell  wall);  K,  surface  view  of  slit-like  pit  com- 
mon in  wood  fibres. 

woods  (i.e.,  Magnolia  [Plate  VI,  Fig.  3],  Hamamelis  and  Liquid- 
ambar  in  part)  are  merely  much-elongated  bordered  pits  which 
appear  as  horizontal  clefts  with  only  narrow  portions  of  the  wall 
between  them  (Fig.  11,  E). 

The  pit  cavities  of  two  adjacent  pits  are  separated  by  the 
primary  wall  which  persists  as  a  limiting  membrane  (Fig.  11,  p.m.). 


34  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

This  membrane,  which  is  really  made  up  of  two  membranes  of 
contiguous  cells  which  have  become  united  in  development,  is 
very  thin  toward  the  border  of  the  pit,  but  usually  thickened 
near  the  centre.  This  thickened  portion  is  called  the  torus  (Fig. 
11,  t).  The  pit  membrane  very  frequently  increases  in  size  and 
bulges  out  so  that  the  torus  lies  lid-like  against  the  aperture  of 
the  pit  canal  (Fig.  11,  A').  A  sieve-like  structure  of  the  pit 
membranes  has  been  observed  in  the  bordered  pits  of  the  vessels 
in  certain  species.* 

Between  the  bordered  pits  on  the  radial  walls  of  the  tracheids 
of  Gymnosperms  it  is  very  common  to  find  folds  of  cellulose,  which, 
when  properly  stained,  are  quite  conspicuous  under  the  compound 
microscope.  These  folds,  which  appear  as  horizontal  or  more  or 
less  semi-circular  markings,  sometimes  doubled,  are  most  abundant 
in  the  thin-walled  tracheids  of  the  early  wood.  They  are  without 
diagnostic  value. 

The  apparent  function  of  pits  is  to  facilitate  the  passage  of  some 
part  of  the  cell  contents  from  one  cell  to  another.  Bordered  pits 
are  mostly  associated  with  water  transfer,  and  simple  pits  with 
the  distribution  of  elaborated  food. 

Pits  are  of  considerable  value  for  systematic  purposes.  For 
example,  in  the  white  pines  and  Pinus  resihosa,  the  radial  wall 
of  each  ray-parenchyma  cell  shows  one  or  two  large  simple  pits 
communicating  with  each  adjacent  wood  tracheid,  while  in  the 
foxtail  and  nut  pines  and  in  the  hard  pines  there  are  three  to 
six  rather  small  pits  so  communicating  (Figs.  4-7) .  The  presence 
of  pits  in  the  tangential  walls  of  the  tracheids  of  the  late  wood 
in  soft  pines,  and  their  absence  in  similar  location  in  the  pitch 
pines,  serve  as  an  additional  point  of  distinction  between  these 
two  great  groups. 

While  the  pits  in  the  radial  walls  of  the  tracheids  of  Gymno- 
sperms are  usually  in  a  single  row,  they  may  occur  in  biseriate 
or  triseriate  arrangement.  In  the  larger  tracheids  of  Tsuga  they 
are  mostly  biseriate.  In  Taxodium  distichum  they  are  characteris- 
tically crowded,  flattened,  and  often  irregularly  arranged. 

In  dicotyledonous  woods  as  a  whole,  pits  are  much  smaller 
and  less  regular  in  their  distribution  than  in  Gymnosperms.    The 


*  Jonsson,  Bengt.  :  Siebahnliche  Poren  in  den  trachealen  Xylemele- 
menten  der  Phanerogamen,  hauptsachlich  der  Leguminosen,  Berichte  d. 
deutschen  Botanischen  Gesellschaft,  Vol.  X,  1892,  pp.  494-513. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES  35 

nature  of  the  pits,  whether  simple  or  distinctly  bordered,  in  the 
walls  of  the  wood  fibres,  and  the  character  of  pitting  where  vessels 
are  in  contact  with  wood  parenchyma  or  the  rays,  are  often 
helpful  in  classification.  Scalariform  bordered  pits  in  the  walls 
of  the  vessels  of  Magnolia  (Plate  VI,  Fig.  3)  serve  to  distinguish 
this  genus  from  Liriodendron  (Plate  VI,  Fig.  4),  in  which  they 
are  absent  or  very  sparingly  developed. 

References 
DeBary,  A.:  Comparative  Anatomy,  pp.  158-164. 
Gregory,  E.  L.:  The  Pores  [Pits]  of  the  Libriform  Tissue,  Bui.  Torrey  Bot. 

Club,  N.  Y.,  Vol.  XIII,  1886,  pp.  197-204;  233-244. 
Penhallow,  D.  P.:  North  American  Gymnosperms,  pp.  59-77. 
Solereder,  H. :  Anatomy  of  the  Dicotyledons,  Vol.  II,  pp.  1139-41. 
Gerry,  Eloise:  The  Distribution  of  the  "Bars  of  Sanio"  in  the  Coniferales, 

Annals  of  Botany,  Vol.  XXIV,  No.  93,  January  1910,  pp.  119-123. 
Kreuz,  J. :    Die  gehoften  Tiipfel  des  Xylems  der  Laub-  und   Nadelholzer, 

Sitzb.  d.  Akad.  Wiss.,  Wien,  Vol.  LXXVI,  Part.  1,  1878,  pp.  353-384. 
Russow,   E. :  Zur  Kenntnis  des  Holzes,  insonderheit  des  Coniferenholzes, 

Bot.  Centralblatt,  Vol.  XIII,  Nos.  1-5,  1883. 


It  is  not  uncommon  to  find  the  vessels  of  many  Dicotyledons 
(Plate  III,  Figs.  3,  4)  and  the  resin  ducts  of  certain  Gymnosperms 
more  or  less  completely  filled  with  pith-like  cells  called  tyloses. 
Usually  the  walls  of  the  tyloses  are  very  thin,  but  exceptions  occur 
(e.g.,  Robinia  and  Toxylon)  where  they  may  be  considerably 
thickened,  sometimes  becoming  sclerotic.  Tyloses  in  large  vessels 
are  plainly  visible  to  the  unaided  eye,  their  high  lustre  giving 
them  the  appearance  of  froth. 

Tyloses  are  cells  which  have  developed  from  protrusions  of  the 
wood  or  ray  parenchyma  into  the  lumen  of  a  vessel  or  the  canal 
of  a  duct  or  an  intercellular  space.  Their  formation  is  apparently 
due  to  differences  in  pressure  within  the  parenchyma  cells  and  the 
vessels  or  ducts  they  adjoin.  After  vessels  lose  their  sap  they  are 
no  longer  turgid,  in  fact  the  air  within  them  becomes  rarefied.  In 
consequence  of  this  reduction  of  pressure  the  neighboring  paren- 
chyma cells  rupture  or  disorganize  the  limiting  membranes  of  the 
pits,  thereby  rendering  the  lumen  of  the  vessel  available  for  their 
further  extension  and  development.  This  explains  why  tyloses 
do  not  occur  in  vessels  which  are  in  a  state  of  activity,  but  as  a 


36  ECONOMIC    WOODS    OF   THE    UNITED    STATES 

general  rule  arise  in  the  inner  region  of  the  sapwood,  i.e.,  in  the 
wood  where  the  vessels  are  losing  their  power  of  conduction.  Once 
inside  the  vessel,  the  intruding  cells  rapidly  divide  and  grow  until 
the  space  is  filled  or  their  food-supply  is  exhausted,  and  thus  form 
a  parenchymatous  tissue  in  which  carbohydrates  may  be  stored. 

The  effect  of  the  formation  of  tyloses  is  to  block  up  the  vessels 
and  render  the  heartwood  impervious,  or  nearly  so,  to  the  entrance 
of  fluids.  Tyloses  are  especially  abundant  in  the  vessels  of  white 
oaks  (Frontispiece),  thus  adding  to  the  technical  value  of  the 
wood  for  cooperage.  This  feature  is  also  of  some  value  in  sepa- 
rating the  white  from  the  black  oaks,  since  in  the  latter  group 
tyloses  are  rather  scarce  or  wanting  (Plate  II,  Fig.  6) .  In  Quercus 
marilandica,  however,  tyloses  are  abundant. 

Tyloses  also  occur  occasionally  in  the  tracheids  of  the  wood  of 
Gymnosperms,  particularly  in  the  wood  of  the  roots.  Tyloses 
in  resin  ducts  are  characteristic  of  Pinus  and  (in  less  degree)  Picea, 
but  are  sparingly  developed  or  absent  in  Larix  and  Pseudotsuga. 

References 
Kirsch,  Simon:  On  the  Development  and  Function  of  Certain  Structures  in 

the  Stipe  and  Rhizome  of  Pteris  aquilina  and   Other  Pteridophytes, 

Trans.  Royal  Soc.  of  Canada,  3d  Series,  Vol.  I,  sec.  iv,  Ottawa,  1908, 

pp.  403-8. 
DeBary,  A.:  Comparative  Anatomy,  p.  170. 
Sachs,  Julius:  Lectures  on  the  Physiology  of  Plants  (trans,  by  H.  Marshal 

Ward),  p.  581. 
Chrysler,  M.  A.:  Tyloses  in  Tracheids  of  Conifers,  New  Phytologist,  No.  7, 

1908,  pp.  198-204. 
Golden,  K.  E.:  Tyloses  in  Brosimum  aubletii,  Proc.  Ind.  Acad.  Sci.,  1904, 

pp.  227-232. 
von  Alten,  H. :  Kritische  Bemerkungen  und  neue  Ansichten  iiber  die  Thyllen, 

Bot.  Zeitung,  Vol.  LXVII,  1909,  pp.  1-23. 
Raatz,  Wilhelm  :  Ueber  Thyllenbildungen  in  den  Tracheiden  der  Conif eren- 

holzer,  Ber.  d.  deutschen  Bot.  Gesellschaft,  Vol.  X,  1892,  pp.  183-192. 

PITH   FLECKS    OR   MEDULLARY   SPOTS 

Pith  flecks  or  medullary  spots  are  small,  brown  or  grayish, 
half-moon-shaped  patches  appearing  so  commonly  on  the  cross 
sections  of  many  diffuse-porous  woods,  especially  of  the  four 
families  Salicacem,  Betulacece,  Rosacece,  and  Aceracece.     On  longi- 


ECONOMIC    WOODS    OF   THE    UNITED    STATES  37 

tudinal  sections  of  a  stem  the  pith  flecks  appear  as  flattened  strands 
running  up  and  down  the  stem,  and  often  into  the  root.  Examined 
microscopically,  pith  flecks  are  seen  to  be  made  up  of  irregularly 
shaped,  polyhedral,  parenchymatous  cells  with  thick,  dark- 
colored  walls  copiously  pitted  with  simple  pits.  At  certain  seasons 
the  cells  are  filled  with  starch  grains. 

Pith  flecks  have  a  pathological  origin.  They  are  due  to  the 
work  of  cambium  miners  whose  tunnels  are  filled  by  the  tylosal 
development  of  adjacent  uninjured  parenchyma  cells,  especially 
of  the  cortex.  The  dissolved  cell  fragments  and  larval  excrement 
are  pressed  into  a  narrow  border  by  the  rapid  growth  and  division 
of  the  "filling  cells." 

This  feature  has  frequently  been  used  for  purposes  of  classifi- 
cation, principally  because  of  the  failure  to  understand  its  exact 
nature.  It  has  been  noted  in  a  large  number  of  woods,  but  is  by 
no  means  constant  in  its  occurrence.  Some  stems,  for  example, 
contain  numerous  pith  flecks,  while  other  individuals  of  the  same 
species  in  the  vicinity,  or  even  from  the  same  root  stock,  do  not 
show  them.  Furthermore,  in  stems  with  pith  flecks  certain  growth 
rings  may  be  free  of  them,  while  others  of  the  same  section  are 
thickly  dotted,  or  the  lower  portion  of  the  stem  may  contain 
them  and  the  upper  be  entirely  free. 

Taken  in  connection  with  other  features,  however,  the  presence 
of  pith  flecks  in  abundance  may  serve  to  indicate  the  species. 
For  example,  they  are  usually  very  numerous  in  Betula  populifolia 
and  B.  papyrifera,  and  infrequent  in  B.  lenta,  B.  lutea,  and  B.  nigra, 
numerous  in  Acer  rubrum  and  A.  saccharinum,  but  usually  want- 
ing in  A.  saccharum. 

References 

Record,  S.  J.:  Pith  Flecks  or  Medullary  Spots  in  Wood,  Forestry  Quarterly, 

Vol.  IX,  No.  3,  1911,  pp.  244-252. 
Grossenbacher,  J.  G.:  Medullary  Spots:  A  Contribution  to  the  Life  History 

of  Cambium  Miners,  Tech.  Bui.  No.  15,  N.  Y.  Agri.  Exp.  Sta.,  Geneva, 

N.  Y.,  1910. 
Von  Tubeuf,  Karl  F.:    Die  Zellgiinge  der  Birke  und  anderer  Laubholzer, 

Forstlich-naturw.  Zeitschrift,  VI.  Jahrgang,  1897,  pp.  314-319.     Also 

Naturw.  Zeitschrift  f.  Forst-  und  Landwirtschaft,  6.  Jahrgang,  1908, 

pp.  235-241. 
Kienitz,   M.:  Die  Entstehung  der   "  Markflecke,"   Bot.   Centralblatt,  Vol. 

XIV,  1883,  pp.  21-26;    56-61. 


38 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


trabecule:  sanio  s  beams 

In  radial  and  cross  sections  of  the  wood  of  all  Gymnosperms 
it  is  not  uncommon  to  find  small  bars  stretched  across  the  lumina 
of  the  tracheids  from  one  tangential  wall  to  another.  Occasionally 
they  appear  in  isolated  tracheids,  but  usually  traverse  in  the  same 
direction  the  entire  length  of  a  long  radial  series  (Fig.  12).  While 
the  most  common  form  of  bar  is  a  simple  cylinder  slightly  enlarged 
at  the  points  of  contact  with  the  cell  wall,  they  may  occur  as 


Iff™ 

®        1 

©          n® 

rliyirill0 

B 


Fig.  12.  —  Trabecule  in  Pinus  murrayana  (lodgepole  pine).  A,  cross  section 
showing  tracheids  with  beams  (tr.)  crossing  the  middle  row  in  tangential  series;  B, 
radial  section  showing  beams  (tr.)  which  become  wider  in  late  wood.  Magnified  about 
150  diameters. 

double  bars  or  as  constricted  plates.  These  bars,  which  were 
first  described  by  Sanio  (loc.  cit.),  originate  in  the  cambium  and 
result  from  the  partial  resorption  of  folds  in  the  cell  wall.  Their 
function  is  unknown.  Owing  to  their  general  distribution  through- 
out all  species  of  Gymnosperms  they  are  without  taxonomic  value. 


References 
Sanio,  Carl:  Botanische  Zeitung,  Vol.  XXI,  No.  14,  1863,  p.  117. 
Muller,    Carl:  Ueber  die   Balken  in  den  Holzelementen  der  Coniferen, 

Bericht    ii.  d.   Verhandlungen  d.  achten  General-Versammlungen  d. 

deutsehen  Botanischen  Gesellschaft,  1890,  pp.  (17)  to  (46). 
Raatz,  Wilhelm:   Die  Stabbildungen  in  secundaren  Holzkorper  der  Baume 

und  die  Initialentheorie,   Jahrb.   fur  Wissenschaftliche  Botanik,  Vol. 

XXIII,  1892,  pp.  567-636. 


ECONOMIC   WOODS    OF   THE    UNITED   STATES  39 


RIPPLE   MARKS 

There  are  numerous  woods  which  present  on  longitudinal  sec- 
tion (particularly  the  tangential)  fine,  delicate  cross  lines  or  stripes 
sometimes  called  "ripple  marks."  The  distance  between  these 
markings  varies  from  0.11  to  0.50  mm.,  and  is  fairly  constant 
for  a  species.  On  some  woods  (e.g.,  /Esculus  octandra,  Swietenia 
mahagoni,  and  Diospyros  virginiana  [Plate  IV,  Figs.  4,  5]),  these 
lines  are  very  clear  and  distinct  to  the  unaided  eye;  on  others 
{e.g.,  Tilia  americana,  T.  pubescens,  and  T.  heterophylla)  they  are 
near  the  limit  of  vision,  or  again,  they  are  invisible  without  the 
lens.  In  most  species  showing  these  markings  the  feature  is  con- 
stant and  of  considerable  importance  for  diagnostic  purposes, 
though  in  a  few  species  (e.g.,  Swietenia  mahagoni)  the  same  piece 
of  wood  may  show  the  markings  in  one  place  and  not  in  another. 

This  cross-striping  of  a  wood  is  due  (1)  to  the  arrangement 
of  the  rays  in  horizontal  series,  or  (2)  to  the  tier-like  ranking  of 
the  wood  fibres,  vessel  segments,  or  other  elements,  or  (3)  to  a 
combination  of  (1)  and  (2)  (Plate  IV,  Figs.  4,  5).  The  lines 
resulting  from  the  horizontal  seriation  of  the  rays  is  usually  more 
conspicuous  and  of  more  common  occurrence  than  those  in  (2). 
In  the  combination  of  the  two  forms,  which  is  very  common,  the 
junction  of  the  vessel  segments  or  of  the  fibres  is  usually  between 
the  rays  (Plate  IV,  Fig.  5). 

This  peculiar  arrangement  of  wood  elements  is  also  evidenced 
on  cross  section.  Where  the  rays  are  in  perfect  horizontal 
seriation  a  section  between  two  tiers  shows  an  entire  absence  of 
rays.  In  most  instances,  however,  it  results  in  gaps  of  irregular 
width,  depending  upon  the  regularity  of  the  stories.  Where  the 
rays  are  much  wider  near  the  middle  than  at  the  margin,  their 
apparent  width  when  viewed  transversely  will  show  considerable 
variation,  according  to  the  relative  location  of  the  plane  of  sec- 
tion. Where  the  fibres  are  arranged  in  tiers,  their  apparent  size 
is  affected  in  a  similar  manner. 

References 

Record,  S.  J.:  Tier-like  Arrangement  of  the  Elements  of  Certain  Woods, 
Science,  January  12,  1912,  pp.  75-77. 

Von  Hohnel,  Franz  Ritter:  Ueber  stockwerkartig  aufgebaute  Holzkorper. 
Sitzb.  d.  Math.  Naturw.  Classe  d.  kaiserlichen  Akademie  d.  Wissen- 
schaften,  Vol.  LXXXIX,  Part  1,  Wien,  1884,  pp.  30-47. 


40  ECONOMIC   WOODS    OF   THE    UNITED    STATES 

Von  Hohnel,  Franz  Ritter:  Ueber  den  etagenformigen  Aufbau  einiger 
Holzkorper,  Berichte  d.  deutschen  Bot.  Gesellschaft,  Vol.  II,  Berlin, 
1884,  pp.  2-5. 

GROWTH    RINGS 

A  tree  increases  in  diameter  by  the  formation  between  the 
old  wood  and  the  inner  bark  of  new  woody  layers  which  envelop 
the  entire  stem  and  living  branches.  In  cross  section,  as  on  the 
end  of  a  log,  these  layers  appear  as  concentric  zones  or  rings 
(Fig.  1).  The  distinction  between  contiguous  rings  is  due  to 
structural  peculiarities,  augmented  in  some  instances  by  local 
deposit  of  resin  or  pigment.  Each  ring  consists  of  two  more  or 
less  readily  distinguishable  parts,  the  inner,  called  early  wood 
(spring  wood),  and  the  outer,  or  late  wood  (summer  or  autumn 
wood). 

In  ring-porous  woods  (Frontispiece;  Plate  III),  such  as  Quercus, 
Castanea,  Fraxinus,  and  Robinia,  the  larger  vessels  become  local- 
ized in  the  early  wood,  thus  forming  a  region  of  more  or  less  open 
and  porous  tissue,  while  the  wood  fibres  preponderate  in  the  late 
wood,  thereby  producing  a  much  denser  layer.  In  other  instances, 
as  in  Acer,  Magnolia,  JEsculus,  and  Liquidambar  (Plate  VI),  where 
the  vessels  are  fairly  uniformly  distributed — diffuse-porous — the 
occurrence  of  growth  rings  may  be  due  to  one  or  more  of  the 
following  conditions:  (1)  a  gradual  diminution  in  size  of  the 
vessels  toward  the  periphery  of  the  ring;  (2)  a  decided  reduction 
in  number  of  the  vessels  in  the  late  wood;  (3)  a  change  in  kind  of 
the  wood  elements,  e.g.,  where  the  outer  layer  of  late  wood  consists 
wholly  or  chiefly  of  wood  parenchyma  or  of  tracheids;  (4)  increase 
in  thickness  of  the  wall  of  the  wood  elements  near  the  limit  of  the 
late  wood. 

In  Gymnosperms  where  vessels  are  wholly  absent  growth  rings 
are  due  to  variations  in  the  tracheids.  Viewed  in  cross  section 
the  cells  of  early  wood  are  relatively  large,  thin-walled,  and  more 
loosely  aggregated;  while  those  of  the  late  wood  are  smaller, 
thicker-walled,  closely  packed  together  and  very  often  radially 
flattened,  presumably  as  a  result  of  cortical  pressure  (Fig.  8; 
Plate  II,  Figs.  1, 2, 4).  This  transition  from  open  to  dense  structure 
may  be  gradual,  as  in  the  soft  pines,  or  very  abrupt,  as  in  many 
hard  pines.  Not  infrequently  the  dense  aggregation  of  cells 
involves  a  deepening  of  the  color  peculiar  to  the  tissue  as  a  whole. 
In  any  wood  it  is  almost  invariably  the  apposition  of  the  more  open 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  41 

early  wood  to  the  face  of  the  more  compact  late  wood  that  serves 
to  define  the  zones  of  growth. 

The  origin  of  growth  rings  is  physiological.  Plants,  like 
animals,  seem  incapable  of  indefinitely  sustained  activity,  but 
require  periods  of  recuperation.  In  latitudes  of  decided  seasonal 
changes  such  periods  of  rest  are  provided  by  the  alternation  of  the 
seasons,  in  which  case  the  zones  of  growth  correspond  very  closely 
with  annual  periods.  This  constancy  of  relation  diminishes 
towards  the  equator  and,  although  in  the  tropics  growth  rings  are 
not  uncommon,  they  provide  no  reliable  index  to  the  age  of  the 
tree.  In  temperate  climates  trees  occasionally  produce  secondary  or 
false  rings,  usually  attributable  to  some  disturbance  of  the  normal 
course  of  growth  of  the  season,  such  as  the  action  of  frost,  drought, 
hail,  and  insect  damages.  Such  rings,  however,  can  usually  be 
distinguished  from  annual  rings  by  their  less  pronounced  line  of 
demarcation. 

Variation  in  width  of  different  growth  rings  is  common  to  all 
trees,  and  is  determined  by  external  conditions  of  light,  heat, 
moisture,  and  available  food-supply.  The  cross  section  of  a  stem 
presents  in  the  variable  form  and  size  of  its  rings  a  history  of  its 
growth  and  nutrition. 

The  breadth  of  an  individual  growth  ring  may  not  be  uniform 
all  round  in  consequence  of  unequal  acceleration  of  the  growth 
on  different  sides,  the  ring  thus  becoming  undulating  or  eccentric. 
The  growth  centre  is  accordingly  not  coincident  with  the  geometric 
centre.  The  more  nearly  erect  the  stem  and  the  more  nearly  per- 
fect the  crown,  the  more  closely  will  the  two  centres  coincide.  In 
some  species  {e.g.,  Carpinus  caroliniana  and  Juniperus  virginiana) , 
irregularity  of  growth  causes  the  trunks  to  become  fluted  or  even 
deeply  scalloped. 

The  growth  rings  near  the  centre  of  a  stem  usually  exhibit 
considerable  difference  in  structure  from  those  later  formed.  The 
elements  are  usually  thinner-walled,  of  shorter  length,  and  less 
densely  aggregated,  so  that  the  inner  core  of  wood  is  comparatively 
soft  and  weak.  In  the  wood  of  Dicotyledons,  although  the  elements 
characteristic  of  the  species  are  all  present,  their  characteristic  ar- 
rangement does  not  appear  clearly  until  later.  This  is  particularly 
evident  in  the  distribution  of  the  vessels  and  wood  parenchyma  in 
many  woods.  Consequently,  in  the  employment  of  these  features 
for  systematic  purposes,  it  is  important  to  use  stems  of  consid- 
erable thickness  rather  than  small  branches  or  young  shoots. 


42 


ECONOMIC    WOODS    OF   THE    UNITED    STATES 


In  ring-porous  woods  of  good  growth  it  is  usually  the  middle 
portion  of  the  ring  in  which  the  thick-walled,  strength-giving 
fibres  are  most  abundant.  As  the  breadth  of  the  ring  diminishes, 
this  middle  portion  is  reduced  so  that  very  slow  growth  (fine 
grain)    produces    comparatively    light,    porous   wood    composed 


Fig.  13. — Quercus  macrocarpa  (bur  oak) :  cross  section  through  three  entire 
growth  rings  showing  very  large  pores  in  early  wood  and  general  absence  of  dense- 
walled  wood. fibres.  Such  wood  is  light,  soft,  and  not  strong.  Magnified  20 
diameters.     (From  Bui.  102,  U.  S.  Forest  Service.) 

Fig.  14. — Quercus  macrocarpa  (bur  oak) :  cross  section  through  one  entire 
growth  ring  and  parts  of  two  others,  showing  comparatively  small  pores  (v)  in 
early  wood  (e.  w.),  and  presence  of  abundant  thick-walled  wood  fibres  in  the  late 
wood  (I.  w.).  Such  wood  is  heavy,  hard,  and  strong.  Magnified  20  diameters. 
(From  Bui.  102,  U.  S.  Forest  Service.) 


mostly  of  thin-walled  vessels  and  wood  parenchyma  (Figs.  13,  14). 
This  explains  why  "second-growth"  (i.e.,  rapidly  grown)  hickory, 
ash,  and  chestnut  are  stronger  than  the  slowly  grown  "virgin" 
stock  of  the  same  species.  Moreover,  in  trees  of  this  type  there 
is  less  early  wood  formed  at  the  base  of  a  stem  than  farther  up, 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  43 

because  growth  begins  considerably  later  at  the  base.  The 
strongest,  densest,  and  toughest  timber  is  that  grown  in  the  open 
where  conditions  are  favorable  to  rapid  growth. 

In  diffuse-porous  woods,  such  as  Acer,  Betula,  Liriodendron, 
and  Fagus,  there  seems  to  be  no  definite  relation  between  ring 
width  and  density.  In  Gymnosperms,  as  a  rule,  wood  of  medium 
to  fine  grain  contains  a  greater  proportion  of  late  wood  and  con- 
sequently possesses  greater  weight  and  strength  than  when  very 
fine  or  very  coarse  grained. 

In  this  connection  the  following  statement  of  H.  Mayr  *  is 
interesting:  "Assuming  identity  of  soil,  the  specific  weight  and 
hardness  of  wood  decreases  with  distance  from  the  optimum 
climate  of  its  production  both  toward  cooler  or  warmer  climates. 
It  is  indifferent  whether  the  annual  zones  consequently  increase 
or  decrease  in  breadth,  or  whether  the  wood  is  broadleaved  or 
coniferous.  Within  the  natural  habitat  of  any  tree  the  centre 
of  its  habitat  produces  the  heaviest  and  hardest  wood." 

Various  theories  have  been  advanced  to  explain  the  formation 
of  early  and  late  wood.  Penhallow  (following  Sachsf)  says  that 
the  elements  of  the  early  wood  are  "formed  under  a  minimum 
tension  in  consequence  of  which  they  rapidly  attain  to  relatively 
great  size,  and  it  is  therefore  found  that  the  first  tissue  of  the 
season  is  always  most  open.  In  consequence  of  the  great  excess 
of  nutrition  supplied  during  this  period  of  growth,  and  the  very 
rapid  process  of  construction  which  follows,  secondary  growth 
of  the  walls  is  limited,  and  these  structures  remain  thin,  while  the 
lumens  are  correspondingly  large." 

R.  Hartig  maintains  that  the  thin-walled  early  wood  is  due 
to  poorer  nutrition  and  the  necessity  of  forming  conductive  tissue, 
while  thick-walled  late  wood  results  from  better  nutriment  during 
the  warm  and  sufficiently  moist  summer.  Wieler,  on  the  other 
hand,  claims  that  the  more  unfavorable  the  conditions  of  nutri- 
tion, the  slower  the  development  of  assimilating  organs,  hence  the 
more  late  wood. 

References 
Penhallow,  D.  P.:  The  Relation  of  Annual  Rings  to  Age,  Can.  Records  of 
Sci.,  Vol.  I,  p.  162. 

:  North  American  Gymnosperms,  pp.  24-32. 

DeBary,  A.:  Comparative  Anatomy,  pp.  475-478;   500-507. 

*Schlich's  Manual  of  Forestry,  Vol.  V,  rev.  ed.,  p.  54. 
t  Text-Book  of  Botany,  p.  575,  foot-note. 


44  ECONOMIC    WOODS    OF   THE    UNITED    STATES 

Roth,  Filibert:  Timber,  Bui.  10,  U.  S.  Div.  of  Forestry,  pp.  14-16. 

Zon,  Raphael:  Methods  of  Determining  the  Time  of  Year  at  which  Timber 

was  Cut,  For.  Quarterly,  Vol.  VIII,  1908. 
Buckhout,  W.  A.:  The  Formation  of  the  Annual  Ring  of  Wood  in  the  Euro- 
i,  pean  Larch  and  the  White  Pine,  For.  Quarterly,  Vol.  V,  No.  3,  Sept. 

1907,  pp.  259-267. 
Dacherowski,  A.:  Type  and  Variability  in  the  Annual  Wood  Increment  of 

Acer  rubrum,  L.  Ohio  Nat.  8,  pp.  343-349,  1908. 
Nordlinger,  H.:  Die  Holzringe  als  Grundlage  des  Baumkorpers,  Stuttgart, 

1872. 
Sanio,  Carl:  Botanische  Zeitung,  Vol.  XXI,  No.  50,  1863,  pp.  391-399. 
Hartig,   R.:  Lehrbuch  der  Anatomie  und   Physiologie   der   Pflanzen,   pp. 

261-263. 

HEARTWOOD    AND    SAPWOOD 

The  course  of  development  of  the  various  wood  elements  is 
fundamentally  the  same,  viz.,  they  are  formed  in  the  cambium, 
they  increase  in  size,  their  walls  thicken  more  or  less,  they  function 
as  living  cells  for  a  time,  but  eventually  lose  their  protoplasmic 
contents  and  die.  Their  change  from  a  living  to  a  dead  condition 
is  ordinarily  not  followed  by  immediate  decay,  and  the  cells 
continue  to  perform  the  mechanical  function  of  support.  The 
parenchyma  cells  remain  alive  for  a  longer  time  than  the  other 
elements. 

The  outer  layers  of  growth  of  a  tree,  especially  one  of  con- 
siderable thickness,  contain  the  only  living  elements  of  the  wood 
and  comprise  the  sapwood.  There  is  usually  a  sharp  line  of 
demarcation  between  the  living  elements  of  the  sapwood  and  the 
non-living  elements  of  the  heartwood,  though  the  vigor  of  the 
living  cells  gradually  wanes  as  their  distance  from  the  cambium 
increases.  The  thickness  of  sapwood  varies  widely  in  different 
species,  in  different  individuals,  in  different  portions  of  a  single 
tree,  and  often  on  different  radii  of  any  particular  section.  Thin 
sapwood  is  characteristic  of  certain  genera,  for  example  Catalpa, 
Robinia,  Toxylon,  Sassafras,  Morus,  Gymnocladus,  Juniperus,  and 
Taxus,  while  in  others  such  as  Hicoria,  Acer,  Fraxinus,  Celtis, 
and  Fagus,  thick  sapwood  is  the  rule. 

The  fact  that  sapwood  occupies  the  peripheral  layers  of  the 
stem  causes  it  to  form  a  considerable  proportion  of  the  volume. 
The  percentage  of  sapwood  to  total  volume  of  the  stem  is  for 
certain   species   approximately   as   follows:  Pinus   palustris,   40; 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  45 

P.  heterophylla,  50;  P.  tceda,  55;  P.  strobus,  30;  Tilia  americana, 
65;  Juniperus  virginiana,  25;  Liriodendron  tulipij 'era,  20;  Quercus 
alba,  20;   Robinia  pseudacacia,  12. 

In  the  same  species  there  generally  exists  a  constant  relation 
between  the  crown  space  and  the  cross-sectional  area  of  the 
sapwood  in  the  stem.  Rapidly  growing  trees  and  trees  in  the  open 
have  a  larger  proportion  of  sapwood  than  those  of  the  same  species 
growing  in  less  open  stands.  In  the  latter  case  the  number  of 
rings  in  the  sapwood  is  almost  always  greater. 

Heartwood  in  general  is  of  a  darker  color  than  sapwood,  due 
to  the  presence  of  gums,  resins,  and  other  substances.  In  some 
genera,  however,  there  is  little  difference  in  appearance  between 
these  two  portions,  for  example,  in  Nyssa,  Ilex,  Celtis,  Populus, 
Salix,  Picea,  Abies,  and  Tsuga. 

Change  from  sapwood  to  heartwood  is  never  accompanied  by 
increased  lignification.  Deposition  of  large  amounts  of  gum  or 
resin  materially  increases  the  weight  of  the  wood,  and  on  that 
account  in  certain  tropical  species  the  heartwood  averages  fully 
one-third  heavier  than  the  sapwood. 

While  physiologically  heartwood  is  that  portion  of  the  woody 
cylinder  which  does  not  contain  living  elements,  yet  technically 
only  discolored  parts  are  so  called,  though  it  of  course  is  without 
living  elements.  Branches  form  heartwood  as  soon  as  they  cease 
to  grow  vigorously,  no  matter  in  what  part  of  the  crown  they  are 
located.  In  a  whorl  one  branch  may  be  practically  all  heartwood 
while  none  of  the  others  shows  any. 

Usually  heartwood  is  commercially  more  valuable  than  sap- 
wood,  partly  on  account  of  its  color,  but  more  especially  because 
of  its  greater  durability  under  exposure.  In  grading  lumber 
sapwood  is  often  considered  a  defect.  Important  exceptions  are 
found  in  the  use  of  paper  birch  for  spools,  hickory  and  ash  for 
handles,  spokes,  etc.,  woods  for  manufacture  of  pulp,  and  timber 
to  be  impregnated  with  preservatives,  where  heartwood  is  con- 
sidered undesirable. 

The  average  thickness  of  the  sapwood  and  the  character  of  the 
demarcation  between  heartwood  and  sapwood  are  features  fre- 
quently made  use  of  in  classification. 

References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  of  Forestry,  p.  13. 
Boulger,  G.  S.:  Wood,  p.  17. 


46  ECONOMIC    WOODS    OF   THE    UNITED    STATES 

DeBart,  A.:  Comparative  Anatomy,  pp.  507-511. 

Munch,  Ernst:     Ueber  krankhafte  Kembildung,  Naturw.    Zeitschrift   fur 

Forst-und  Landwirtschaft,  8.    Jahrgang,  1910,  pp.  533-547;  553-569. 
Nordlinger,    H.:  Die    Technischen   Eigenschaften   der   Holzer,    Stuttgart, 

1860,  pp.  28-40. 

GRAIN   AND    TEXTURE 

Grain  is  a  general  term  used  in  reference  to  the  arrangement 
or  direction  of  the  wood  elements  and  to  the  relative  width  of 
the  growth  rings.  To  have  specific  meaning  it  is  essential  that 
it  be  qualified.  The  kinds  of  grain  commonly  described  are  fine, 
coarse,  even,  uneven,  rough,  smooth,  straight,  cross,  spiral,  twisted, 
wavy,  curly,  mottled,  landscape,  bird's-eye,  gnarly,  and  silver. 

Coarse  grain  applies  to  woods  of  rapid  growth,  i.e.,  it  denotes 
wide  rings;  fine  grain,  to  woods  of  slow  growth.  Even  and  uneven 
apply  respectively  to  regularity  or  irregularity  of  the  growth  rings; 
rough  and  smooth,  to  the  manner  in  which  wood  works  under  tools. 
Straight  grain,  as  applied  to  a  tree,  occurs  when  the  wood  ele- 
ments are  parallel  to  the  axis  of  growth;  as  applied  to  a  board, 
when  the  radial  and  tangential  planes  of  structure  are  parallel 
to  its  length.  Sawn  boards  or  timbers  are  often  cross-grained 
even  when  cut  from  straight-grained  logs  while  straight-grained 
pieces  may  be  split  from  spiral-grained  trees.  The  strength  of 
a  piece  of  timber,  particularly  in  bending,  rapidly  weakens  as  the 
plane  of  its  fibres  deviates  from  a  direction  parallel  to  its  length. 
On  this  account  split  timber  is  usually  stronger  than  when  sawn, 
a  fact  made  use  of  in  wood-working.  For  instance,  billets  for 
handles  and  blocks  for  telegraph-insulator  pegs  are  invariably 
split. 

It  is  not  uncommon  in  any  tree,  and  usual  in  many  cases,  for 
the  wood  elements  to  be  arranged  spirally  about  the  central  axis. 
The  spiral  may  run  to  the  right  or  left,  but  the  direction  is  usually 
fairly  constant  within  a  species.  Various  theories  have  been 
advanced  to  explain  the  phenomenon  of  spiral  growth  or  torsion. 
The  one  most  commonly  accepted  considers  the  obliquity  of  the 
fibres  a  method  of  accommodating  the  increase  in  length  of  the 
cells  after  their  formation  in  the  cambium.  There  seems  to  be 
ground  for  suspecting  that  wind  may  have  an  influence  on  this 
spiral  development.  For  instance,  trees  of  Larix  americana  have 
been  observed  which,  though  straight-grained  while  young,  had 


ECONOMIC   WOODS    OF   THE    UNITED    STATES  47 

developed  spirally  twisted  growth  layers  after  the  trees  were 
thirty  to  forty  years  old,  when,  unprotected  by  associated  trees, 
they  were  subjected  to  heavy  winds.  There  is  a  further  possibility 
that  some  species  have  an  inherent  tendency  to  develop  twisted 
stems.  In  any  event,  when  such  stems  are  sawn  the  lumber  is 
cross-grained  and  usually  unfit  for  use  where  strength  is  required. 
The  extent  of  the  defect  depends  upon  the  pitch  of  the  spiral. 

When  the  elements  interweave  and  are  not  constant  in  one 
general  direction,  wood  is  also  said  to  be  cross-grained,  though 
the  term  spiral  grain  or  interlocked  grain  is  more  applicable.  Often 
this  condition  does  not  interfere  with  tangential  splitting.  Wood 
with  interlocked  fibres  is  tough  and  not  necessarily  weakened, 
but  always  tends  to  warp  and  twist  in  seasoning.  Examples  occur 
in  Nyssa,  JEsculus,  Liquidambar,  and  Eucalyptus. 

Wavy  grain  and  curly  grain  result  when  the  fibres  undulate 
but  do  not  cross  each  other.  When  the  undulations  are  large  the 
grain  is  said  to  be  wavy;  when  small,  curly.  Usually  the  waves 
are  on  the  radial  plane  and  tangential  splitting  produces  a  smooth 
surface,  showing  the  grain  to  advantage.  Such  grain  is  common 
in  Acer,  JEsculus,  Fraxinus,  Prunus,  and  Betula.  It  is  most 
common  near  the  roots  and  at  the  insertion  of  large  branches. 

Silver  grain  is  produced  by  quarter-sawing  timber  in  which 
the  rays  are  sufficiently  high  to  show  readily  on  radial  surface. 
The  appearance  of  the  rays  adds  very  materially  to  the  value  of 
woods  for  cabinet  work  and  furniture.  Species  which  exhibit 
conspicuous  silver  grain  are  Quercus  (all  species,  but  particularly 
Q.  alba),  Platanus  occidentalis,  Fagus  americana,  and  to  a  less 
extent  Acer  saccharum,  Prunus  serotina,  and  Swietenia  mahagoni. 

Texture  is  a  term  which  refers  to  the  relative  size,  quality,  or 
fineness  of  the  elements  as  affecting  the  structural  properties  of 
a  wood.  Like  grain,  it  requires  qualifying  adjectives  to  attain 
specific  meaning.  The  most  common  attributes  of  texture  are 
fineness  and  coarseness,  evenness  and  unevenness.  Coarse  texture 
applies  to  woods  with  many  large  elements,  or  the  average  size  of 
which  is  large,  for  example,  Caslanea,  Gymnocladus,  Sequoia.  In 
fine  texture  the  opposite  condition  prevails,  as  in  Juniperus, 
/Esculus,  Salix,  Populus. 

Even  texture  or  uniform  texture  are  terms  used  to  describe 
woods  whose  elements  exhibit  little  variation  in  size,  for  example, 
Taxodium  (Plate  II,  Fig.  1),  Juniperus  (Plate  II,  Figs.  3,  4), 
Sequoia,  /Esculus  (Plate  VI,  Fig.  5).     Uneven  texture  applies  to 


north  r  LIBRARY 
JV.  C.  State  College 


48  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

the  opposite  condition,  such  as  is  common  in  all  prominently 
ring-porous  woods  (Frontispiece;  Plate  III),  (e.g.,  Quercus,  Cas- 
tanea,  Ulmus,  Fraxinus),  and  in  other  woods  with  decided  differ- 
ences between  early  and  late  wood  (e.g.,  Pinus  palustris,  P.  tceda, 
and  Pseudotsuga). 

Texture  and  grain  are  terms  very  commonly  confused  in 
popular  usage.  The  distinctions  as  above  expressed  will  obviate 
the  difficulty  resulting  from  the  attempt  to  make  the  term  "grain" 
too  comprehensive. 

Reference 

Record,  S.  J.:  Grain  and  Texture  in  Wood,  Forestry  Quarterly,  Vol.  IX, 
No.  1,  1911,  pp.  22-25  (reprinted  in  Woodcraft,  June  1911). 

KNOTS 

Branches  originate,  as  a  rule,  at  the  central  axis  of  a  stem  and, 
while  living,  increase  in  size  by  the  addition  from  year  to  year 
of  woody  layers  which  are  a  continuation  of  those  in  the  stem. 
From  this  it  follows  that  the  form  of  the  included  portion  or  knot 
approaches  that  of  a  cone  with  its  apex  inward. 

During  the  development  of  a  tree  most  of  the  limbs,  especially 
the  lower  ones,  die,  but  persist  for  a  time — often  for  a  great  many 
years.  Subsequent  layers  of  growth  of  the  stem  are  not  intimately 
joined  with  the  fibres  of  the  dead  limb,  but  are  laid  around  its 
base.  Hence  dead  branches  produce  loose  knots  which  may  drop 
out  after  the  tree  has  been  cut  into  lumber. 

The  stubs  of  dead  limbs  that  have  broken  off  are  usually 
occluded  by  subsequent  growth  so  that  the  outer  surface  of  the 
bole  is  smooth  or  clear,  especially  toward  the  butt.  The  interior 
of  all  stems  is  more  or  less  knotty,  but  in  butt  logs  the  knots 
are  fewest  and  smallest.  Sometimes  knots  enhance  the  value  of 
timber  for  cabinet  work  and  interior  finish,  by  giving  it  a  pleasing 
figure.  Material  cut  near  the  junction  of  a  large  limb  or  at  the 
base  of  a  crotch  usually  exhibits  very  handsome  grain. 

Knots  materially  affect  checking  and  warping,  ease  in  working, 
and  cleavability  of  timber.  They  are  defects  which  weaken  timber 
and  depreciate  its  value  for  structural  purposes  where  strength  is 
an  important  consideration.  The  weakening  effect  is  much  more 
serious  where  timber  is  subjected  to  bending  and  tension  than 
where  under  compression.  The  extent  to  which  a  knot  affects 
the  strength  of  a  beam  depends  upon  its  position,  size,  direction 


ECONOMIC    WOODS    OF   THE    UNITED    STATES  49 

of  fibre,  and  condition.  A  knot  on  the  upper  side  is  compressed, 
while  one  on  the  lower  side  is  subjected  to  tension.  The  knot, 
especially  (as  is  often  the  case)  if  there  is  a  season  check  in  it, 
offers  little  resistance  to  tensile  stress.  Small  knots,  however, 
may  be  so  located  in  a  beam  as  actually  to  increase  its  strength 
by  tending  to  prevent  longitudinal  shearing.  Knots  in  a  board 
or  plank  are  least  injurious  when  they  extend  through  it  at  right 
angles  to  its  broadest  surface.  Knots  apparently  have  little 
effect  on  the  stiffness  of  timber. 

"At  the  junction  of  limb  and  stem  the  fibers  on  the  upper  and 
lower  sides  of  the  limb  behave  differently.  On  the  lower  side 
they  run  from  the  stem  into  the  limb,  forming  an  uninterrupted 
strand  or  tissue  and  a  perfect  union.  On  the  upper  side  the  fibers 
bend  aside,  are  not  continuous  into  the  limb,  and  hence  the 
connection  is  imperfect. 

"Owing  to  the  arrangement  of  the  fibers,  the  cleft  made  in 
the  splitting  never  runs  into  the  knot  if  started  on  the  side  above 
the  limb,  but  is  apt  to  enter  the  knot  if  started  below,  a  fact  well 
understood  in  woodcraft."  * 

Sound  knots  are  as  hard  as,  and  usually  considerably  harder 
than,  the  wood  surrounding  them.  In  coniferous  woods  they  are 
commonly  highly  resinous,  and  in  finished  lumber  are  apt,  on  that 
account,  to  fail  to  retain  paint  or  varnish.  When  such  trees 
decay  the  knots  remain  sound  and  are  prized  for  fuel.  In 
grading  lumber  and  structural  timber,  knots  are  classified  accord- 
ing to  their  character  (sound,  loose,  encased),  size  (pin,  standard, 
large),  and  direction  of  fibre  (round,  spike). 

References 
Roth,  Filibert:    Timber,  Bui.  10,  U.  S.  Div.  For.,  1859,  pp.   23,   41,   44 

48,  49. 
Cline,  McGarvey,  and  Knapp,  J.  B.:  Properties  and  Uses  of  Douglas  Fir, 

Bui.  88,  U.  S.  Forest  Service,  1911,  pp.  32-37. 

DENSITY   AND    WEIGHT 

Density  of  wood  varies  widely  in  different  species,  in  different 
individuals,  and  even  in  different  portions  of  the  same  tree. 
The  specific  gravity  f  of  wood  substance  is  about  1.6;   hence  the 

*  Roth,  loc.  cit.,  p.  23. 

t  By  specific  gravity  is  meant  the  ratio  of  the  weight  of  thoroughly  dried 
4 


50  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

reason  any  wood  floats  in  water  is  because  of  the  buoyancy  of  the 
air  imprisoned  in  its  elements  and  spaces.  When  this  air  is  dis- 
placed by  water  the  wood  becomes  "waterlogged,"  and  will  no 
longer  float.  The  greater  the  proportion  of  cell  wall  the  greater 
the  density;  consequently  late  wood  is  denser  and  of  higher  specific 
gravity  than  early  wood,  and  the  greater  the  proportion  of  late 
wood  the  denser  the  wood  as  a  whole.  Woods  composed  largely 
of  thick-walled,  narrow-lumined  fibres  are  always  dense  and 
heavy.  Other  things  being  equal,  the  weight  of  wood  is  a  good 
criterion  of  its  hardness  and  strength. 

In  practice  the  weight  of  wood  is  calculated  from  small, 
sound  specimens  which  have  been  oven-dried  at  a  temperature  of 
100°  C.  (the  boiling-point  of  water)  until  they  reach  a  constant 
weight.  Since  weight  is  subject  to  wide  variations,  the  single 
value  usually  assigned  to  a  species  is  really  the  average  of  a  large 
number  of  determinations  and  is  applicable  only  in  a  general  way. 
If  a  wood  weighs  less  than  thirty  pounds  per  cubic  foot  it  is  con- 
sidered light;  if  between  thirty  and  forty  pounds,  medium  light 
or  medium  heavy;   and  if  more  than  forty  pounds,  heavy. 

The  lightest  wood  in  the  United  States  is  that  of  Leitneria 
floridana,  the  specific  gravity  of  which  is  0.21  for  body  wood  and 
0.15  for  root  wood.  The  wood  of  Condalia  ferrea  has  a  specific 
gravity  of  1.3;  that  of  Guaiacum  sanctum  1.14.  From  the  inves- 
tigation of  429  American  species,  as  published  in  the  report  of 
the  Tenth  Census  of  the  United  States,  it  appears  that  242  species, 
including  most  of  the  commercial  woods,  lie  between  0.45  and 
0.75  in  specific  gravity. 

TABLE  III 

One  Hundred  and  Fifty  Trees  of  the  United  States  Arranged  in 
Order  of  the  Average  Specific  Gravity  of  Their  Dry  Woods 
(Tenth  Census). 

Species  Sp.  Gr. 

Quercus  prinoides 86 

Quercus  chrysolepis 85 

Hicoria  alba S4 

Ostrya  virginiana 83 


Sp.  Gr. 

Condalia  ferrea 1 .  30 

Guaiacum  sanctum 1 .  14 

Quercus  virens 95 

Quercus  texana 91 


wood  to  an  equal  volume  of  water  at  its  greatest  density,  which  occurs  at  a 
temperature  of  4°  C.  (39.2°  F.).  A  cubic  foot  of  pure  water  at  this  temperature 
weighs  62.43  pounds.  Dividing  the  weight  in  pounds  of  a  cubic  foot  of 
wood  by  62.43  will  give  the  specific  gravity  of  the  wood. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


51 


TABLE 
Species  Sp.  Gr. 

Quercus  agrifolia 83 

Hicoria  glabra 82 

Cornus  florida 82 

Hicoria  laciniosa 81 

Quercus  michauxii 80 

Hicoria  myristicseformis 80 

Pinus  serotina 79 

Diospyros  virginiana 79 

Toxylon  pomiferum 77 

Quercus  laurif olia 77 

Prosopis  juliflora 77 

Betula  lenta 76 

Quercus  imbricaria 75 

Pinus  heterophylla 75 

Quercus  prinus 75 

Ulmus  alata 75 

Quercus  phellos 75 

•Quercus  alba 75 

Quercus  macrocarpa 75 

Ilex  decidua 74 

Hicoria  aquatica 74 

Larix  occidentalis 74 

Quercus  coccinea 74 

Robinia  pseudacacia 73 

Quercus  nigra 73 

Celtis  occidentalis 73 

Carpinus  caroliniana 73 

Swietenia  mahagoni 73 

Ulmus  racemosa 73 

Ulmus  crassifolia 72 

Quercus  aquatica 72 

Prunus  americana 72 

Crataegus  crus-galli 72 

Fraxinus  quadrangulata 72 

Hicoria  olivaef ormis 72 

Juniperus  monosperma 71 

Fraxinus  lanceolata 71 

Quercus  velutina 70 

Pinus  palustris 70 

Ulmus  pubescens 70 

Quercus  palustris 69 

Gymnocladus  dioicus 69 

Acer  saccharum 69 

Fagus  americana 69 

Gleditsia  triacanthos 67 

Betula  lutea 66 

Fraxinus  americana 65 


III — Continued 


Species  Sp.  Gr. 

Quercus  rubra 65 

Ulmus  americana 65 

Taxus  brevif olia 64 

Pinus  edulis 64 

Magnolia  grandiflora 64 

Nyssa  sylvatica 64 

Taxus  floridana 63 

Cupressus  macrocarpa 63 

Fraxinus  pennsylvanica 63 

Larix  americana 62 

Acer  rubrum 62 

Juglans  nigra 61 

Pinus  echinata 61 

Betula  papyrif era 60 

Liquidambar  styraciflua 59 

Morus  rubra 59 

Castanea  pumila 59 

Juniperus  pachyphlcea 58 

Prunus  serotina 58 

Ilex  opaca 53 

Juniperus  occidentalis 58 

Betula  nigra 58 

Betula  populifolia 58 

Fraxinus  oregona 57 

Platanus  occidentalis 57 

Pinus  monophylla 57 

Castanopsis  chrysophylla 56 

Pinus  aristata 56 

Juniperus  utahensis 55 

Pyrus  americana 55 

Pinus  taeda 54 

Pinus  balfouriana 54 

Magnolia  macrophylla 53 

Pinus  inops 53 

Pinus  jeffreyi 53 

Pseudotsuga  taxifolia 52 

Pinus  rigida 52 

Tumion  taxifolium 51 

Sassafras  sassafras 50 

Magnolia  glauca 50 

iEsculus  calif ornica 50 

Juniperus  virginiana 49 

Pinus  resinosa 49 

Alnus  oregona 48 

Chamsecyparis  nootkatensis  ...      .48 

Tumion  californicum 48 

Pinus  ponderosa 47 


52 


ECONOMIC   WOODS   OF   THE    UNITED   STATES 


TABLE  III— Continued 


Species  Sp.  Gr. 

Abies  magnifica 47 

Magnolia  acuminata 47 

Populus  grandidentata 46 

Chamsecyparis  lawsoniana 46 

Picea  nigra 46 

Abies  nobilis 46 

Taxodium  distichum 45 

^Esculus  glabra 45 

Tilia  americana 45 

Castanea  dentata 45 

Catalpa  catalpa 45 

Salix  nigra 45 

Pinus  flexilis 44 

Acer  negundo 43 

Picea  sitchensis 43 

vEsculus  octandra 43 

Salix  discolor 43 

Tilia  heterophylla 43 

Tsuga  canadensis 42 

Liriodendron  tulipif era 42 

Abies  amabilis 42 

Sequoia  sempervirens 42 

Catalpa  speciosa 42 

Pinus  albicaulis 42 


Species  Sp.  Gr. 

Pinus  coulteri 41 

Pinus  murrayana 41 

Populus  heterophylla 41 

Juglans  cinerea 41 

Tilia  pubescens 41 

Picea  alba 41 

Populus  tremuloides 40 

Libocedrus  decurrens 40 

Asimina  triloba 40 

Alnus  oblongifolia 40 

Pinus  glabra -39 

Pinus  monticola 39 

Pinus  strobus 38 

Abies  balsamea 38 

Populus  trichocarpa 38 

Thuya  plicata 38 

Pinus  lambertiana 37 

Abies  concolor 36 

Populus  balsamifera 36 

Abies  grandis 35 

Picea  engelmanni 34 

Thuya  occidentalis 32 

Sequoia  washingtoniana 29 

I  Leitnena  floridana 21 


References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  Forestry,  pp.  25-28. 

Sargent,  C.  S.:  Forests  of  North  America,  Part  9,  Tenth  Census  of  the  U.  S., 

Washington,  1884,  pp.  248-251. 
Gayer,  K:  Schlich's  Manual  of  Forestry,  Vol.  V,  1908,  pp.  50-65. 
Nordlinger,  H.:  Die  Technischen  Eigenschaften  der  Holzer,  Stuttgart,  1860, 

pp. 115-227. 

WATER    CONTENT   OF   WOOD 


Water  occurs  in  living  sap  wood  in  three  states,  viz.,  (1)  in 
the  protoplasmic  contents  of  the  cells,  (2)  in  the  cell  walls,  and  (3) 
as  free  water  wholly  or  partially  filling  the  iumina  of  cells,  fibres, 
and  vessels  that  have  lost  their  contents.  In  heartwood  water 
normally  exists  only  in  condition  (2).  In  the  fresh  sapwood  of 
Pinus  strobus,  which  may  be  taken  as  fairly  typical,  water  com- 
prises about  half  of  the  total  weight  and  is  distributed  approx- 


ECONOMIC   WOODS    OF   THE    UNITED    STATES  53 

imately  as  follows:  in  contents  of  living  cells,  5  per  cent;  satu- 
rating cell  walls,  35  per  cent;   free  water,  60  per  cent. 

In  a  living  tree  the  wood  nearest  the  bark  contains  the  most 
water.  If  no  heartwood  is  present  the  decrease  toward  the  pith 
is  gradual;  otherwise  the  change  is  quite  abrupt  at  the  sapwood 
limit.  In  Pinus  palustris,  for  example,  the  weight  of  the  fresh 
wood  within  an  inch  of  the  bark  may  be  50  per  cent  of  water; 
that  between  one  and  two  inches,  only  35  per  cent;  that  of  the 
heartwood,  only  20  per  cent.  The  water  content  of  any  par- 
ticular section  of  a  tree  depends  upon  the  amount  of  sapwood, 
and  is  therefore  greater  for  the  upper  than  for  the  lower  portions 
of  the  stem;  greater  for  limbs  than  bole;  greatest  of  all  in  the 
roots. 

The  water  content  of  wood  can  readily  be  determined  in  the 
following  manner:  saw  off  a  thin  section  of  wood;  weigh  careful- 
ly on  a  delicate  balance;  dry  in  an  oven  at  a  temperature  of  100°  C. 
until  a  constant  weight  is  obtained;  reweigh.  The  difference 
between  the  fresh  weight  and  the  dry  weight  is  the  amount  of 
moisture  contained.     Computed  on  a  basis  of  the  fresh  weight, 

fresh  weight  -  dry  weight 

Per  cent  of  moisture  = — : r-rr X  1UU. 

fresh  weight 

Thus  if  the  weight  of  the  original  block  of  wood  was  twice  the 

final  weight,  there  was  as  much  water  as  wood;   in  other  words, 

one-half,  or  50  per  cent,  of  the  original  weight  was  water.    The 

figures  in  the  preceding  paragraph  are  on  this  basis. 

Computed  on  a  basis  of  dry  weight, 

fresh  weight  -  dry  weight 

Per  cent  of  moisture  =  ^ r-— X  100. 

dry  weight 

In  the  problem  cited  above  the  loss  of  moisture  was  100  per  cent 
of  the  dry  weight.  This  method  furnishes  a  constant  basis  for 
comparison,  while  the  other  varies  with  every  change  in  moisture 
degree.  Subsequent  references  to  the  per  cent  of  moisture  will 
refer  to  computation  on  the  basis  of  dry  weight. 

It  is  impossible  to  remove  absolutely  all  the  water  from  wood 
without  destroying  the  wood.  Wood  is  considered  thoroughly 
dried  when  it  ceases  to  lose  weight  in  a  constant  temperature  of 
100°  C,  though  it  still  retains  2  to  3  per  cent  of  moisture,  and 
if  exposed  to  higher  temperature  will  continue  to  give  up  water. 

Seasoning,  which  is  essentially  drying,  adds  appreciably  to 
the  strength,  and,  in  slightly  less  proportion,  to  the  stiffness  of 


54  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

wood.  A  piece  of  green  spruce  timber,  for  example,  may  become 
four  times  stronger  when  thoroughly  dried.*  This  is  an  extreme 
case,  however,  and  does  not  apply  to  large  timbers  where  check- 
ing, which  always  occurs  to  some  extent,  may  counterbalance 
partially  or  even  entirely  the  gain  in  strength  due  to  drying. 

In  small  forms  of  hardwood  material,  as  implement  and 
carriage  stock,  and  in  coniferous  timber  in  some  forms,  as  cross- 
arms  for  telegraph  poles,  thorough  and  uniform  reduction  of  the 
moisture  content  produces  a  large  increase  in  strength.  In  fact 
a  comparatively  weak  wood  may,  when  perfectly  dry,  be  much 
stronger  than  a  strong  wood  in  a  green  condition.  Consequently 
tests  to  determine  the  mechanical  properties  of  wood  must,  to 
be  comparable,  take  into  consideration  the  moisture  content  of 
the  specimens.  By  means  of  a  great  many  tests  the  relation  of 
the  moisture  degree  to  the  mechanical  properties  can  be  approx- 
imated and  coefficients  or  correction  factors  determined  by  which 
the  strength  value  at  any  given  water  content  can  be  reduced  to 
a  standard  (usually  12  per  cent)  or  other  desired  moisture  degree. f 

Loss  of  water  from  cell  lumina  alone  does  not  affect  the  mechan- 
ical properties  of  wood.  It  is  only  when  the  cell  walls  begin  to 
give  up  their  water  that  increase  in  strength,  stiffness,  hardness, 
and  resilience  occur.  Conversely,  the  absorption  of  water  weakens 
wood  only  to  the  point  where  the  cell  walls  become  completely 
saturated.  This  critical  point  has  been  termed  by  Tiemann 
(loc.  cit.)  the  fibre-saturation  point.  It  varies  with  different  treat- 
ments of  the  wood  and  under  different  conditions.  The  water 
content  at  this  point  is  greater  in  wood  previously  dried  and 
especially  in  wood  which  has  been  subjected  to  high  temperature 
than  it  is  in  green  wood.  The  amount  of  moisture  at  the  fibre- 
saturation  point  in  green  wood  of  various  species  has  been  found 
by  Tiemann  (loc.  cit.)  to  be  between  20  and  30  (average  about  27) 
per  cent. 

The  water  content  of  wood  materially  affects  durability. 
Since  decay  is  produced  by  fungi,  and  to  a  less  extent  by  bacteria, 
both  of  which  require  considerable  water  for  their  development, 

*  In  comparing  the  strength  and  stiffness  of  wood  in  green  and  dry  condi- 
tions, the  fact  should  be  borne  in  mind  that,  owing  to  shrinkage,  dry  wood  is 
more  compact  and  contains  a  greater  amount  of  wood  substance  per  unit  of 
volume  than  green  wood. 

t  Such  tables  have  been  prepared  for  several  of  the  commercial  woods  of 
the  United  States.     (See  Bui.  70  and  Cir.  108,  U.  S.  Forest  Service.) 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  55 

all  that  is  necessary  to  render  even  the  most  perishable  wood 
indefinitely  immune  from  decay  is  to  keep  it  dry.  Wood  con- 
taining not  more  than  10  per  cent  of  moisture  will  not  decay. 

Rate  of  seasoning  differs  with  the  kind  of  wood  and  with 
its  shape.  A  thin  piece  dries  more  rapidly  than  a  thicker  one; 
sap  wood  more  rapidly  than  heartwood;  a  light,  open  wood  more 
readily  than  one  that  is  dense  and  heavy.  Large  beams  or  logs 
are  exceedingly  slow  in  drying,  requiring  from  two  to  several 
years'  seasoning  in  the  open  air  before  reaching  an  air-dry  condi- 
tion in  the  interior.  Ties  require  from  three  months  to  a  year 
to  season,  depending  on  the  kind  of  timber  and  the  climate. 
Much  depends  upon  the  method  of  piling,  since  boards  in  open  piles 
often  dry  twice  as  fast  as  those  in  solid  piles. 

As  a  result  of  numerous  experiments  by  the  U.  S.  Forest 
Service  upon  large  beams  of  Pinus  palustris  and  P.  toeda,  the 
following  conclusions  were  reached  (Bui.  70,  p.  123) : 

"  (1)  The  drying-out  process  takes  place  almost  wholly  through 
the  faces  of  the  beam  and  not  longitudinally,  except  near  the  ends. 

"  (2)  The  ratio  of  evaporation  through  a  surface  is  proportional 
to  the  rate  of  growth  or  density  of  the  wood  near  the  surface, 
being  most  rapid  in  the  case  of  sap  wood. 

"  (3)  If  the  whole  stick  is  made  up  of  heartwood  or  the  pro- 
portion of  sapwood  is  uniform  throughout,  the  longitudinal  dis- 
tribution of  moisture  is  very  regular.  If  the  proportion  of  sap- 
wood  is  not  uniform,  on  the  other  hand,  the  portion  containing 
the  most  sap  is  the  most  susceptible  to  moisture  influences;  i.e., 
it  will  dry  or  will  absorb  moisture  the  most  rapidly. 

"The  average  of  two  cross-sections  of  longleaf  pine  sticks, 
12  by  12  inches  and  8  by  16  inches  and  16  feet  long,  which  were 
air-dried  for  two  years,  showed  an  average  moisture  content  in 
the  outer  portion,  cut  halfway  from  surface  to  centre,  of  17.7 
per  cent,  while  the  inner  part  contained  25.7  per  cent. 

"From  this  it  is  quite  evident  that  where  timber  of  structural 
sizes  is  used,  the  strength  ordinarily  reckoned  upon  should  not 
be  greater  than  that  of  the  green  condition." 

References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  Forestry,  pp.  29-31. 
Tiemann,  H.  D.:  The  Effect  of  Moisture  upon  the  Strength  and  Stiffness  of 
Wood,  Bui.  70,  U.  S.  Forest  Service,  1906,  p.  144. 


5(5  ECONOMIC    WOODS    OF   THE    UNITED    STATES 

Tiemann,  H.  D.:    The  Strength  of  Wood  as  Influenced    by  Moisture,  Cir 

cular  108,  U.  S.  Forest  Service,  1907,  p.  42. 
Johnson,  J.  B.:  Timber  Physics,  Part  II,  Bui.  8,  U.  S.  Div.  of  Forestry 

1893,  pp.  22-24. 

SHRINKAGE,    WARPING,    AND    CHECKING 

The  volume  of  wood  is  maximum  when  the  cell  walls  are 
saturated  with  water.  When  this  condition  exists  the  presence 
or  absence  of  free  water  in  the  cell  cavities  and  the  intercellular 
spaces  does  not  affect  the  volume.  When  the  cell  walls  begin 
to  dry,  they  become  thinner,  but  do  not  contract  to  an  appreciable 
extent  longitudinally.  A  dry  wood  cell  is  therefore  of  practically 
the  same  length  as  it  was  in  a  green  or  saturated  condition,  but 
is  smaller  in  cross  section,  has  thinner  walls  and  a  larger  lumen. 
According  to  Nageli's  hypothesis,  the  cell  wall  is  composed  of 
aggregations  in  crystalline  form  of  minute  parts  or  micellae,. 
These  micellce  are  separated  by  films  of  water  which  become 
thinner  as  the  wall  dries  and  thicker  as  it  swells.  This  shrinkage 
is  roughly  proportional  to  the  thickness  of  the  walls,  and  in  con- 
sequence the  denser  woods  or  the  denser  portions  of  a  wood 
shrink  more  than  those  less  dense. 

Inasmuch  as  wood  is  not  a  homogeneous  substance,  but  an 
intricate  structure  composed  of  cells  exhibiting  from  moderate 
to  extreme  variation  in  shape,  size,  thickness  of  walls,  and  more, 
especially  in  arrangement,  it  follows  that  shrinkage  cannot  be 
uniform  throughout  any  specimen.  Late  wood,  being  denser, 
shrinks  more  than  early  wood.  The  ray  cells,  with  their  longest 
diameters  for  the  most  part  at  right  angles  to  the  direction  of  the 
other  elements,  oppose  radial  shrinkage  and  tend  to  produce 
longitudinal  shrinkage  of  wood.  Only  in  the  tangential  direc- 
tion are  these  otherwise  opposing  forces  parallel.  For  this  reason 
as  well  as  the  fact  that  the  denser  bands  of  late  wood  are 
tangentially  continuous,  while  radially  they  are  separated  by 
alternate  zones  of  less  dense  early  wood,  wood  usually  shrinks 
more  than  twice  as  much  tangentially  as  it  does  radially.  In 
all  cases,  however,  shrinkage  parallel  to  the  vertical  axis  is  very 
slight,  one-tenth  to  one-third  of  one  per  cent,  and  is  maximum 
in  woods  with  curly  or  wavy  grain  or  with  large  or  very  abundant 
rays. 

The  following  table  gives  the  results  of  a  series  of  shrinkage- 


ECONOMIC    WOODS    OF   THE    UNITED    STATES 


57 


tests  made  by  Mr.  Hugh  P.  Baker  at  the  Yale  Forest  School. 
The  figures  given  represent  the  average  shrinkage  resulting 
from  reducing  green  wood  to  a  kiln-dry  condition  and  are  com- 
puted on  the  basis  of  the  original  measurements. 


TABLE  IV 
Shrinkage  of  Wood  along  Different  Dimensions 


Species. 

Length 

% 

Radius 

% 

Diameter 

Circum- 
ference 

% 

Area  of 
cross 
section 

% 

Volume 

% 

Juniperus  virginiana 

Castanea  dentata 

0.32 
.25 
.24 
.04 
.36 
.15 
.10 

2.7 
3.0 
3.7 
7.4 
2.9 
4.3 
6.1 

2.5 
3.2 
3.5 

7.5 
3.1 
4.8 
6.2 

5.6 
4.9 
8.2 
9.2 
6.9 
9.3 
11.5 

6.9 
11.2 
10.4 
19.4 

7.3 
12.6 
17.1 

5.9 

19.8 

7.6 

13.7 

1S.0 

Liriodendron  tulipifera.  .  . 
Nyssa  sylvat  ica 

Irregularities  in  shrinkage  tend  to  cause  wood  to  become 
distorted  or  warped.  In  woods  with  straight  grain  and  uniform 
texture  the  tendency  to  warp  is  minimum  unless  the  distribution 
of  the  moisture  content  is  very  unequal.  Thus  the  upper  surface 
of  a  green  board  exposed  to  the  hot  rays  of  the  sun  will  dry  much 
more  rapidly,  and  therefore  becomes  shorter  than  the  lower  side, 
causing  the  board  to  curl  up  at  the  ends.  Woods  with  interlaced 
fibres  or  with  cross  or  spiral  grain  {e.g.,  Nyssa,  Liquidambar, 
Eucalyptus)  always  shrink  unequally,  and  consequently  require 
careful  handling  in  drying  to  prevent  serious  deformation.  Warp- 
ing clue  to  unequal  distribution  of  moisture  may  subsequently 
be  overcome  by  thorough  drying,  but  the  deformation  resulting 
from  great  irregularity  of  structure  is  usually  permanent. 

In  Fig.  15  is  shown  in  somewhat  exaggerated  manner  the 
deformation  caused  by  the  greater  tangential  shrinkage.  The  flat 
side  of  a  log  cut  through  the  middle  becomes  convex  (B).  Boards 
cut  from  half  of  a  log  assume  the  form  shown  in  (C),  while  a  plank 
from  the  middle  of  a  log  becomes  convex  on  both  sides.  This 
explains  most  of  the  difference  in  shrinkage  of  timbers  and  boards 
of  different  sizes,  shapes,  and  manner  of  sawing  (i.e.,  whether 
plain  or  quarter-sawed). 

When  the  strains  due  to  unequal  shrinkage  can  no  longer 


58 


ECONOMIC   WOODS   OF   THE   UNITED    STATES 


be  accommodated  by  the  plasticity  of  the  wood  substance,  cracks 
or  checks  are  formed.  These  are  most  common  along  the  rays, 
since  there  the  strains  are  greatest  and  most  complex.  However, 
when  the  strength  of  the  rays  is  greater  than  the  cohesive  force 
<of  the  cementing  substance  uniting  the  two  layers  of  the  primary 
-cell  wall,  radial  fracture  passes  through  the  median  plane  of  the 
primary  wall  of  the  wood  cells  instead  of  along  the  ray. 

Variation  in  moisture  content  due  to  irregular  drying  results 
in  checks,  most  of  which  are  temporary,  and  as  equilibrium 
becomes  again  established  gradually  close  and  become  imper- 
ceptible. The  more  rapidly  wood  is  dried,  the  greater  is  the 
tendency  to  check,  for  even  if  evaporation  could  be  controlled 
so  as  to  proceed  uniformly  throughout  the  specimen,  the  cells 
would  not  be  given  sufficient  time  to  adjust  themselves  to  the 


Fig.  15. — Effects  of  shrinkage.  A,  plank  cut  from  middle  of  log  (boxed 
heart),  showing  double-convex  surfaces  and  large  season  check  through  upper 
half.  B,  log  cut  in  half,  showing  the  flat  'surface  becoming  convex  and  the  appear- 
ance of  three  large  season  checks.     C,  half  of  a  log  cut  into  boards  showing  warping. 

changed  conditions.  The  presence  of  checks  in  wood,  no  matter 
how  imperceptible,  always  impairs  the  strength  of  the  material. 

If  the  outer  portion  of  a  piece  of  wood,  especially  hard  wood, 
dries  much  more  rapidly  than  the  inner,  a  hard  shell  is  formed 
on  the  outside,  while  the  interior  retains  most  of  its  original 
moisture.  This  condition  is  known  as  case-hardening.  This  dry 
shell  resists  the  transpiration  of  the  moisture  from  the  interior  and 
retards  drying,  besides  increasing  the  strains  on  the  fibres.  When 
the  interior  finally  dries,  the  internal  strains  frequently  become 
so  great  that  large  checks  open  up,  producing  a  honeycombed 
condition. 

Checks  which  result  from  greater  shrinkage  along  the  tangent 
than  along  the  radius  are  permanent  and  increase  in  size  as  drying 
progresses  (Figs.  1 ;  15  B).  They  cause  serious  difficulty  in  season- 
ing large  timbers  and  especially  material  in  the  round,  such  as 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  59 

logs,  poles,  and  posts.  If  seasoned  too  rapidly  hardwood  timbers 
may  split  entirely  open  so  as  completely  to  destroy  their  value. 
In  handling  such  material  it  is  a  common  practice  to  forestall 
such  checking  by  driving  in  S-shaped  metal  wedges  across  the 
incipient  cracks.  Such  damage  can  also  be  reduced  by  more 
careful  piling  and  handling  of  the  material. 

References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  Forestry,  pp.  32-37. 

Boulger,  G.  S.:  Wood,  pp.  80-88. 

Von  Schrenck,  H.:  Seasoning  of  Timber,  Bui.  41,  U.  S.  Bu.  of  Forestry,  1903, 

p.  48. 
Tiemann,  H.  D.:  Effect  of  Moisture  on  the  Strength  and  Stiffness  of  Wood, 

Bui.  70,  U.  S.  Forest  Service,  pp.  76-79;    116-118;    123. 
Baker,  Hugh  P.:  A  Study  in  the  Shrinkage  of  Wood  (unpublished  thesis, 

Yale  Forest  School,  1904). 
Carrens,  C:    Zur  Kenntniss  der  innern  Structur  der  vegetabilischen  Zell- 

membranen,  Jahrb.  fiir  wissensch.  Botanik,  Vol.  XXIII,   1892,  pp. 

567-636. 
Nageli,  K. :  Ueber  den  innern  Bau  der  Vegetabilischen  Zellenmembranen, 

Sitzb.d.  Akad.  Wiss.,  Miinchen,  1864,  Pt.  1,  282-326;  Pt.  2,  114-170. 

HYGROSCOPICITY 

Wood  substance  has  the  property  of  absorbing  moisture  from 
the  atmosphere.  When  artificially  dried  wood  is  exposed  to  the 
open  air  it  will  increase  in  weight,  due  to  the  addition  of  hygro- 
scopic water.  Although  the^  amount  of  water  thus  attracted  is 
always  greater  than  in  the  surrounding  air,  it  does  not  remain 
constant,  but  varies  with  the  humidity,  and  is  equal  to  8  to  16 
(average  12)  per  cent  of  the  dry  weight  of  the  wood.  These 
variations  are  accompanied  by  proportionate  changes  in  volume, 
that  is,  the  wood  alternately  shrinks  and  swells,  or  u works."1 
Hygroscopicity  can  be  reduced,  but  not  entirely  eliminated,  by 
subjecting  wood  to  boiling,  steaming,  prolonged  soaking,  or 
exposure  to  high  temperature. 

This  property  of  wood  is  a  serious  hindrance  to  its  use  in 
certain  positions  where  exact  fitting  is  permanently  desired. 
Drawers  and  doors  "stick"  in  damp  weather,  and  become  loose 
in  dry  weather,  or  when  artificially  heated  and  dried  for  con- 


60  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

siderable  time.  Furniture,  wainscoting,  interior  finish,  and  cabinet 
work  may  be  badly  damaged  by  prolonged  drying,  which  opens 
up  joints,  loosens  tenons,  and  causes  veneers  to  separate  from 
their  backing.  This  property  may  be  largely  overcome  by  soaking 
wood  in  oil  or  coating  the  surface  with  paint,  oil,  or  varnish, 
which  excludes  most  of  the  air  and  moisture  and  keeps  the  con- 
dition of  the  wood  uniform.  Light,  porous  woods  "work"  less 
than  dense  woods.  On  account  of  their  greater  porosity  and  light- 
ness, slowly  grown  ring-porous  woods  (Fig.  13)  shrink  and  swell 
less  than  specimens  of  the  same  species  more  rapidly  grown 
(Fig.  14). 

The  presence  of  natural  oils,  gums,  and  pigments  such  as  are 
commonly  found  in  the  heartwood  of  many  species  usually  reduces 
the  hygroscopicity  of  woods. 

References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  For.,  pp.  30-31. 

Exner,  W.  F. :  Lorey's  Handbuch  der  Forstwissenschaft,  Vol.  II,  1903,  pp. 

128-129. 
Gayer,  K.:  Schlich's  Manual  of  Forestry,  Vol.  V  (1908),  pp.  66-75. 

PERMEABILITY 

In  all  green  wood  the  cells  are  separated  from  each  other  by  a 
thin  membrane,  the  primary  cell  wall.  The  only  important 
exceptions  are  the  vessels  between  whose  segments  there  is  free 
communication  vertically.  Vessels,  however,  like  other  cells,  are 
separated  from  each  other  and  from  other  elements  by  the  primary 
wall.  This  wall  ordinarily  persists  intact  unless  ruptured  by 
parenchymatous  outgrowths — tyloses.  It  is  permeable  by  water 
and  certain  dilute  solutions  which  filter  through  slowly,  but  is 
impervious  to  oils  and  resins.  Gases  can  enter  into  living  cells 
only  by  going  into  solution,  and  in  that  condition  diosmosing 
through  the  cell  wall. 

These  facts  have  an  important  bearing  on  the  process  of 
impregnating  wood  with  preservatives  to  prevent  decay.  It  is 
not  difficult  to  force  gases  or  fluids  through  open  vessels  of  green 
wood,  but  it  is  impossible  to  do  so  if  they  are  plugged  with  tyloses. 
For  example,  it  is  very  easy  to  blow  through  the  vessels  of  green 
wood  of  most  red  or  black  oaks,  even  in  pieces  of  considerable 
length.     In  green  wood  of  the  white  oaks,  on  the  other  hand, 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  61 

it  is  impossible  to  force  any  air  through  the  vessels,  even  for  short 
lengths  and  with  very  high  pressure,  since  in  this  case  they  are 
blocked  with  tyloses.  Even  in  the  red  or  black  oaks,  however, 
air  cannot  be  forced  through  the  other  elements  of  green  wood. 

When  wood  becomes  dry  its  penetrability  by  both  gases  and 
liquids  is  increased  to  a  remarkable  extent.  The  same  specimen 
of  white  oak  which,  while  green,  effectually  withstood  an  air 
pressure  of  150  pounds  per  square  inch  will,  when  dry,  allow  the 
passage  of  air,  not  only  through  the  vessels,  but  also  the  other 
elements,  under  a  pressure  of  5  pounds  per  square  inch  or  less. 
Similar  effects  are  produced  by  drying  any  wood  beyond  its  fibre- 
saturation  point.  This  fact  emphasizes  the  great  importance  of 
seasoning  wood  before  attempting  to  impregnate  it  with  pre- 
servatives. 

According  to  Tiemann  (loc.  tit.),  the  explanation  of  this 
is  that  the  drying  of  the  cell  walls  causes  minute  checks  or  slits 
to  occur  in  the  primary  walls.  The  dryer  the  wood  becomes  the 
larger  the  slits  and  the  more  permeable  the  wood.  These  slits 
do  not  entirely  close  when  the  wood  is  resoaked,  so  that  wood 
once  dried  cannot  be  restored  to  its  original  condition. 

Steaming  is  said  to  produce  similar  results,  though  the  slits 
apparently  are  not  as  wide  as  when  wood  is  air-dried.  It  is  prob- 
able, however,  that  the  maximum  amount  of  slitting  would  result 
from  thoroughly  drying  wood  that  had  been  previously  steamed. 
Boiling  green  wood  in  oil  results  in  more  or  less  seasoning  of  the 
outer  portions,  thus  allowing  some  penetration  by  the  oil. 

Dry  woods,  however,  differ  greatly  in  penetrability.  Light, 
porous  woods  as  a  rule  are  much  easier  to  impregnate  than  dense, 
compact  ones.  Heartwood  of  any  species  offers  more  resistance 
than  the  sapwood,  due  probably  to  the  presence  in  the  walls  of 
gums,  resins,  and  other  infiltrations.  Tyloses,  which  always 
reduce  penetrability,  are  mostly  absent  from  the  outer  portion  of 
sapwood  even  when  very  abundant  in  the  heartwood  of  the  same 
tree.  In  the  wood  of  Gymnosperms  it  appears  that  the  wood- 
parenchyma  cells  are  more  penetrable  than  the  tracheids.  Open 
resin  ducts  permit  the  entrance  of  fluids  into  the  body  of  the 
wood,  behaving  in  a  manner  similar  to  the  vessels  of  Dicotyledons. 

References 

Bailey,  Irving  W.:  The  Preservative  Treatment  of  Timbers.  I.  The 
Validity  of  Certain  Theories  Concerning  the  Penetration  of  Gases  and 
Preservatives  into  Seasoned  Wood.  For.  Quarterly,  11:  1:  5-11,  Mch. 
1913 


62  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

Bailey,  Irving  W. :  The  Effect  of  the  Structure  of  Wood  upon  its  Permeability, 

No.  1.     The  Tracheids  of  Coniferous  Timbers.     In  Bui.  174,  Am.  Ry. 

Eng.  Assn.,  Feb.  1915. 
Tiemann,  Harry  D.:  The  Physical  Structure  of  Wood  in  Relation  to  Its 

Penetrability  by  Preservative  Fluids,  Bui.  120,  Am.  Ry.  Eng.  and 

Maintenance  of  Way  Ass'n,  Jan.  1910. 


CONDUCTIVITY 

Dry  wood  is  a  very  poor  conductor  of  heat,  as  is  well  illus- 
trated in  its  use  for  matches  and  as  handles  for  utensils  and  tools 
subjected  to  various  temperatures.  Increase  in  density  or  in 
moisture  content  increases  the  conductivity  of  wood.  Woods 
are  most  conductive  in  direction  parallel  to  the  grain  and  least 
so  in  radial  direction,  the  ratio  in  some  instances  being  as  high 
as  2  to  1.  The  difference  between  radial  and  tangential  direc- 
tions in  this  regard  is  slight,  and  is  probably  due  to  the  fact  that 
in  a  tangential  direction  the  bands  of  the  denser  and  therefore 
more  conductive  late  wood  are  continuous,  while  radially  they  are 
interrupted  by  alternate  bands  of  the  less  dense  early  wood. 

Wood  in  a  dry  condition  is  a  non-conductor  of  electricity. 
Increase  of  water  content  reduces  its  value  as  an  insulator.  Light, 
porous  woods  are  more  resistant  to  the  passage  of  electric  currents 
than  are  dense  woods;  highly  resinous  woods,  more  than  woods 
without  resin,  since  resin  and  oil  are  poor  conductors  of  electricity. 

Wood  is  a  good  conductor  of  sound,  particularly  in  a  longi- 
tudinal direction.  The  denser,  the  more  uniform,  and  the  dryer 
the  wood  the  greater  is  its  ability  to  transmit  sound.  Unsound- 
ness and  decay  materially  reduce  this  property. 

References 

Gayer,  Karl:  Schlich's  Manual  of  Forestry,  Vol.  V,  1908,  pp.  78-79. 
Exner,  W.  F. :  Lorey's  Handbuch  der  Forstwissenschaft,  Vol.  II,  p.  117. 
Mathey,  Ali-honse:  Traite  d' Exploitation  Commerciale  des  Bois,  Vol.  I, 

Paris,  1906,  pp.  63-65. 
Nordlinger,  H. :  Die  Technischen  Eigenschaften  der  Holzer,  pp.  56-114. 

RESONANCE 

"If  a  log  or  scantling  is  struck  with  the  ax  or  hammer,  a 
sound  is  emitted  which  varies  in  pitch  and  character  with  the 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  63 

shape  and  size  of  the  stick,  and  also  with  the  kind  and  condition 
of  wood.  Not  only  can  sound  be  produced  by  a  direct  blow, 
but  a  thin  board  may  be  set  vibrating  and  be  made  to  give  a  tone 
by  merely  producing  a  suitable  tone  in  its  vicinity.  The  vibra- 
tions of  the  air,  caused  by  the  motion  of  the  strings  of  the  piano, 
communicate  themselves  to  the  board,  which  vibrates  in  the 
same  intervals  as  the  string  and  reenforces  the  note.  The  note 
which  a  given  piece  of  wood  may  emit  varies  in  pitch  directly  with 
the  elasticity,  and  indirectly  with  the  weight,  of  the  wood.  The 
ability  of  a  properly  shaped  sounding-board  to  respond  freely 
to  all  the  notes  within  the  range  of  an  instrument,  as  well  as  to 
reflect  the  character  of  the  notes  thus  emitted  (i.e.,  whether 
melodious  or  not),  depends,  first  on  the  structure  of  the  wood, 
and  next  on  the  uniformity  of  the  same  throughout  the  board. 
In  the  manufacture  of  musical  instruments  all  wood  containing 
defects,  knots,  cross  grain,  resinous  tracts,  alternations  of  wide 
and  narrow  rings,  and  all  wood  in  which  summer  and  spring 
wood  are  strongly  contrasted  in  structure  and  variable  in  their 
proportions  are  rejected,  and  only  radial  sections  (quarter-sawed, 
or  split)  of  wood  of  uniform  structure  and  growth  are  used. 

"  The  irregularity  in  structure,  due  to  the  presence  of  relatively 
large  pores  and  pith  rays,  excludes  almost  all  our  broad-leaved 
woods  from  such  use,  while  the  number  of  eligible  woods  among 
conifers  is  limited  by  the  necessity  of  combining  sufficient  strength 
with  uniformity  in  structure,  absence  of  too  pronounced  bands 
of  summer  wood,  and  relative  freedom  from  resin. 

"Spruce  is  the  favored  resonance  wood;  it  is  used  for  sounding- 
boards  both  in  pianos  and  violins,  while  for  the  resistant  back 
and  sides  of  the  latter,  the  highly  elastic  hard  maple  is  used. 
Preferably  resonance  wood  is  not  bent  to  assume  the  final  form; 
the  belly  of  a  violin  is  shaped  from  a  thicker  piece,  so  that  every 
fiber  is  in  the  original  in  as  nearly  an  unstrained  condition  as  possi- 
ble, and  therefore  free  to  vibrate.  All  wood  for  musical  instruments 
is,  of  course,  well  seasoned,  the  final  drying  in  kiln  or  warm  room, 
being  preceded  by  careful  seasoning  at  ordinary  temperatures 
often  for  as  many  as  seven  years  or  more.  The  improvement  of 
violins,  not  by  age,  but  by  long  usage,  is  probably  due,  not  only 
to  the  adjustment  of  the  numerous  component  parts  to  each 
other,  but  also  to  a  change  in  the  wood  itself;  years  of  vibrating 
enabling  any  given  part  to  vibrate  much  more  readily."  * 

*  Roth,  F.,  Timber,  Bui.  10,  U.  S.  Div.  For.,  pp.  24-25. 


64  ECONOMIC    WOODS    OF   THE    UNITED    STATES 


COLOR 

When  wood  is  first  formed  it  is  almost,  if  not  entirely,  color- 
less, as  may  be  observed  in  the  outermost  growth  rings  in  any 
species.  After  a  year  or  two  it  usually  becomes  yellowish,  and 
still  later  when  changed  into  heartwood  a  decided  deepening  of 
color  results.  Exceptions  to  this  rule  are  rather  numerous,  for 
example,  Picea,  Tsuga,  Abies,  Salix,  Alnus,  Betula,  Ilex,  and 
Msculus  exhibit  little  or  no  contrast  in  color  between  heartwood 
and  sapwood.  In  all  species  the  sapwood  has  a  very  limited 
range  of  color  and  shade,  but  the  heartwood  exhibits  great  varia- 
tion, from  the  chalky  white  of  Ilex  opaca  to  the  ebony  black  of 
old  Diospyros  virginiana,  with  practically  all  intermediate  colors, 
shades,  and  tints.  In  many  woods  the  demarcation  in  color 
between  heartwood  and  sapwood  is  very  sharp  and  distinct,  while 
in  others  the  transition  is  gradual.  In  some  instances  {e.g., 
Sequoia,  Ilex,  Catalpa,  Cladrastis  luted)  the  color  is  uniform, 
while  in  others  {e.g.,  Liriodendron,  Liquidambar,  Swietenia)  it  is 
variable  not  only  in  different  specimens,  but  in  different  portions 
of  the  same  piece.  The  golden  yellow  of  Toxylon  shows  narrow 
streaks  of  red ;  Liquidambar  shows  black  streaks  that  usually  give 
the  finished  lumber  a  handsome  watered  effect;  Liriodendron 
varies  from  deep  iridescent  blue  to  yellowish  brown;  Robinia 
varies  from  light  straw-colored  to  deep  golden  yellow  like  Toxylon; 
Taxodium  is  sometimes  nearly  black,  often  yellowish,  reddish, 
brown,  or  mottled.  The  deep-colored  wood  of  Juniperus  fre- 
quently exhibits  streaks  of  white  sapwood,  the  intermingling 
resulting  from  the  fluted  periphery  of  the  stem. 

It  is  generally  true  that  depth  of  color  of  woods  is  a  criterion 
of  durability.  Thus  the  dark  heartwood  of  Juniperus,  Sequoia, 
Prosopis,  Toxylon,  Robinia,  and  Morus  is  very  resistant  to  decay, 
while  that  of  Salix,  Populus,  Tilia,  JEsculus,  Acer,  Fraxinus,  and 
Nyssa  is  perishable.  The  deeper  color  of  the  heartwood  is  due 
to  the  infiltration  or  deposition  in  the  cell  walls  and  lumina  of 
gums,  resins,  pigments,  tannin,  and  other  substances.  To  these 
is  ascribed  the  greater  durability  of  wood,  since  sapwood  is 
invariably  not  durable  under  exposure.  In  some  instances,  how- 
ever {e.g.,  Chamcecyparis,  Taxodium,  Catalpa,  Sassafras),  the 
infiltrated  substances  tend  to  prevent  decay  without  greatly 
deepening  the  color  of  the  heartwood. 


ECONOMIC   WOODS    OF   THE    UNITED    STATES  65 

Color  adds  greatly  to  the  value  of  wood  for  interior  finish, 
cabinet  work,  marquetry,  and  parquetry.  It  is  a  very  common 
practice  to  stain  wood  artificially.  Light-colored  and  therefore 
less  valuable  wood  of  mahogany,  such  as  commonly  grows  in  the 
United  States  and  Mexico,  is  often  darkened;  Ilex  opaccf is  readily 
stained  black  to  resemble  ebony;  Betula  lenta,  when  properly 
stained,  is  a  good  imitation  of  mahogany;  in  fact,  by  the  applica- 
tion of  stains  and  finishes  the  variations  in  color  and  shade  that 
can  be  produced  in  woods  is  practically  unlimited.  It  is  also 
possible  by  the  introduction  of  certain  chemicals  to  color  the 
sapwood  of  a  living  tree. 

For  some  uses  of  wood  lack  of  color  is  prized.  This  is  especially 
true  of  pulpwood,  since  coloring  matter,  if  present,  must  be 
bleached  out.  Color  is  also  undesirable  in  certain  grades  of 
flooring.  In  handles  and  spokes  dark  color  is  considered  a  defect, 
since  it  indicates  heartwood,  which  is  usually  (but  erroneously) 
thought  to  be  weaker  than  the  colorless  sapwood. 

All  woods  darken  upon  exposure  to  the  atmosphere,  probably 
due  to  the  oxidation  of  the  coloring  matters.  The  rich  golden 
yellow  of  Toxylon  and  Morus  becomes  a  dark  or  russet  brown; 
the  sapwood  of  Alnus  oregona  turns  reddish  brown;  Pinus  monti- 
cola  and  P.  strobus  often  become  vinous  red,  especially  near  the 
end  of  an  exposed  piece  of  wood.  On  this  account  the  natural 
<3olor  of  a  wood  can  only  be  seen  on  fresh-cut  sections.  Prolonged 
immersion  in  water  causes  wood  to  darken — some  turning  gray, 
others  almost  black. 

Some  woods  (e.g.,  Cladrastis  lutea,  Prosopis,  Sequoia,  Juglans) 
impart  color  to  water  in  which  they  are  soaked.  The  color  of 
many  others  can  be  removed  by  treatment  with  NaOH  or  other 
chemicals,  but  it  is  often  necessary  to  reduce  the  wood  to  pulp 
before  it  can  be  bleached.  Many  tropical  woods  (e.g.,  Clorophora 
tinctoria,  Hcematoxijlon  campechianum,  Ccesalpina,  Pterocarpus) 
contain  coloring  principles  of  value  in  the  arts  for  dyeing,  though 
they  have  been  largely  superseded  by  aniline  dyes.  Of  indigenous 
woods,  Toxylon  pomiferum  and  several  species  of  Xanthoxylum 
are  sometimes  employed  for  this  purpose,  usually  as  adulterants 
of  old  fustic  (Clorophora). 

Color  is  often  of  great  assistance  for  diagnostic  purposes, 

though  the  range  of  variation  and  difficulty  of  description  must 

always  be  taken  into  consideration.    Unless  otherwise  stated,  the 

oolors  mentioned  in  the  key  refer  always  to  the  fresh  cross  section 

5 


DO  ECONOMIC    WOODS    OF    THE    UNITED    STATES 

of  a  piece  of  dry  wood.  The  character  of  the  demarcation  in  color 
between  heartwood  and  sapwood,  whether  sharp  or  gradual,  is 
often  an  important  feature,  though  usually  not  exhibited  on  very 
small  specimens.  The  character  and  amount  of  coloring  matter  ex- 
tracted by  treatment  with  NaOH  is  sometimes  made  use  of  in 
identification. 

Abnormal  discoloration  of  wood  usually  denotes  disease. 
The  black  check  in  Tsuga  heterophylla  is  the  result  of  insect 
attacks.  The  reddish-brown  streaks  so  common  in  Hicoria  are 
mostly  the  result  of  injury  by  birds.  The  bluing  of  the  sapwood 
of  many  soft  woods  is  due  to  the  attacks  of  fungi.  Many  fungi 
can  be  determined  specifically  by  the  characteristic  color  they 
impart  to  wood. 

References 

Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  For.,  p.  24. 

Gayer,  K.:  Schlich's  Manual  of  Forestry,  Vol.  V  (1908),  pp.  43-46. 

Hanausek,  T.  F.:  The  Microscopy  of  Technical  Products. 

Mell,  C.  D.:  Fustic  Wood,  Cir.  1S4,  U.  S.  Forest  Service. 

Exner,  W.  F. :  Lorey's  Handbuch  der  Forstwissenschaft,  Vol.  II,  pp.  105-111. 

Nordlinger,  H. :  Die  Technischen  Eigenschaften  der  Holzer,  pp.  46-51. 

GLOSS    OR   LUSTRE 

Gloss  or  lustre  of  wood  refers  to  the  manner  in  which  light 
is  reflected  by  the  wood  elements.  The  fibres  of  the  bast  are 
more  lustrous  than  the  wood  fibres.  The  fibre  of  flax  is  highly 
lustrous,  while  that  of  cotton  is  dull.  Similar  variation  occurs 
in  the  elements  of  different  woods.  For  example,  the  woods  of 
Fagara,  Rhus,  and  Toxylon  are  highly  lustrous;  those  of  Acer, 
Betula,  and  Robinia  less  so;  while  those  of  Juglans  nigra,  Sequoia, 
Fagus,  and  Platanus  are  dull.  The  wood  of  Picea  possesses  a 
pearly  lustre;  that  of  Guaiacum  and  Taxodium  is  rather  greasy 
or  waxy.  In  some  cases  the  lustre  varies  in  different  parts  of 
the  wood  or  on  different  planes.  The  late  wood  of  Juniperus 
virginiana  exhibits  a  frosted  lustre  on  tangential  surface.  The 
rays  on  quarter-sawed  wood  of  several  species,  particularly  the 
oaks,  are  so  lustrous  in  contrast  to  the  other  elements  as  to  give 
rise  to  the  term  "silver  grain,"  while  the  rays  themselves  are 
called  "mirrors."  Woods  with  high  natural  lustre  are  usually 
capable  of  taking  a  high  polish.     Lustre  is  a  sign  of  soundness 


ECONOMIC    WOODS   OF   THE    UNITED    STATES  67 

in  wood,  for  incipient  decay  causes  wood  to  become  dull  and 
"dead."  Sound  wood  in  thin  sections  is  translucent  and  exhibits 
double  refraction.  The  presence  of  rosin  in  wood  increases  its 
translucency. 

References 

Gayer,  K.:  Schlich's  Manual  of  Forestry,  Vol.  V  (1908),  pp.  47,  79. 
Exner,  W.  F.:  Lorey's  Handbuch  der  Forstwissenschaft,  pp.  111-112. 
Nordlinger,  H. :  Die  Technischen  Eigenschaften  der  Holzer,  pp.  46-51. 


SCENT   OR   ODOR 

Every  wood  when  fresh  possesses  in  some  degree  a  characteristic 
scent,  though  in  a  great  many  cases  it  is  so  weak  or  fleeting  that 
it  escapes  notice.  Odor  depends  upon  chemical  compounds  {e.g., 
ethereal  oils  and  tannin)  which  form  no  part  of  the  wood  itself. 
Ordinarily  it  is  more  pronounced  in  heartwood  than  in  sapwood. 
It  is  also  greater  in  wood  in  a  green  condition  than  when  seasoned, 
more  evident  on  moist  surfaces  than  on  dry.  Upon  prolonged 
exposure  to  air,  or  when  submerged  in  water,  wood  gradually 
loses  its  scent.  In  some  cases  the  loss  is  complete  throughout; 
in  others  only  the  outer  portions  are  affected.  Woods  deriving 
their  odors  from  the  presence  of  ethereal  oils,  as  is  the  case  in 
many  cedars,  apparently  may  be  kept  indefinitely  and  still  emit 
their  characteristic  odors  when  a  fresh  surface  is  exposed. 

Upon  exposure  to  the  air  for  a  short  time  some  green  woods 
(e.g.,  Quercus)  acquire  a  disagreeable,  soured  odor,  probably  due 
to  the  decomposition  of  certain  organic  compounds.  Woods  in 
process  of  decay  emit  various  odors,  sometimes  very  disagreeable 
{e.g.,  Populus),  sometimes  not  unpleasant  {e.g.,  Quercus),  but 
always  different  from  the  natural  scent  characteristic  of  the  sound 
wood. 

The  fumes  of  burning  wood  are  occasionally  characteristic. 
Resinous  woods,  as  Pinus,  give  off  an  odor  of  tar.  The  woods  of 
Juniperus  virginiana  and  Chamcecyparis  lawsoniana  burn  with  a 
pungent,  spicy  scent,  giving  the  latter  a  special  value  for  match- 
sticks.  The  woods  of  Cercidium  and  Parkinsonia  give  off  very 
penetrating,  disagreeable  fumes  when  burned,  reducing  materially 
their  desirability  for  fuel. 

The  scent  of  certain  woods  renders  them  commercially  valuable. 
Cigars  are  believed  to  be  considerably  improved  by  being  kept  in 


b8  economic  woods  of  the  united  states 

cedar  boxes.  The  scent  of  cedar  (Juniperus  virginiana,  Chamce- 
cyparis lawsoniana,  and  C.  nootkatensis)  is  apparently  disagreeable 
to  moths  and  other  insects,  making  the  wood  desirable  for  cabinets, 
wardrobes,  chests,  and  drawers  where  furs  and  woolen  clothes 
are  kept.  Cedar  shavings  are  also  employed  for  the  same  purpose. 
Loss  of  scent  from  the  exposed  surface  of  the  wood  soon  seriously 
impairs  the  efficiency  of  the  wood  for  this  purpose.  For  some 
purposes,  especially  as  receptacles  for  wines,  liquors,  drinking- 
water,  and  oils,  meats,  fish,  butter,  and  other  foodstuffs,  highly- 
scented  wood  is  undesirable  since  it  is  apt  to  taint  the 
contents. 

While  scent  is  often  a  very  valuable  aid  to  the  identification 
of  wood,  its  utility  is  lessened  by  the  difficulty  and  often  impos- 
sibility of  describing  an  odor  so  that  one  unfamiliar  with  it  would 
be  able  to  recognize  it.  Such  descriptions  are  necessarily  limited 
to  comparisons  with  well-known  scents  which  are  usually  inade- 
quate. The  scent  of  the  wood  of  Pinus  is  resinous  or  like  tur- 
pentine; that  of  Juniperus  and  Chamcecyparis  thyoides  aromatic, 
like  cedar  oil;  that  of  Chamcecyparis  nootkatensis,  C.  lawsoniana, 
and  Libocedrus  decurrens  spicy-resinous;  that  of  dark-colored,  waxy 
specimens  of  Taxodium,  like  rancid  butter;  that  of  Catalpa  some- 
what like  kerosene;  that  of  Viburnum  lentago  and  V.  prunifolium 
very  disagreeable  and  pungent. 

The  following  genera  and  species  usually  can  be  recognized 
by  their  odor  alone :  Juniperus,  Chamcecyparis  thyoides,  C.  lawson- 
iana, Lihocedrus,  Thuya,  Tsuga  canadensis,  Sassafras,  Viburnum, 
and  Catalpa.  With  a  keen  sense  of  smell  others  may  be  recog- 
nized; for  example,  Pinus,  Taxodium,  Quercus,  Castanea,  Ulmus, 
and  Betula.  Prominent  among  exotic  species  characterized  by 
pronounced  scents  are  the  camphor  trees  (Cinnamomum  camphora, 
Dryobalanus  camphora,  Camphora  glanduliferum) ,  Indian  sandal- 
wood (Santalum  album),  and  violet-wood  (Acacia  homophylla). 

References 

Gayer,  K:  Schlich's  Manual  of  Forestry,  Vol.  V  (1908),  pp.  47-48. 
Roth,  F.:  Timber,  Bui.  10,  U.  S.  Div.  For.,  p.  24. 
Krais,  Paul:  Gewerbliche  Materialkunde,  Vol.  I,  Die  Holzer,  p.  652. 
Exner,  W.  F.:  Lorey's  Handbuch  der  Forstwissenschaft,  Vol.  II,  pp.  116-117. 
Nordlinger,  H.:  Die  Technischen  Eigenschaften  der  Holzer,  pp.  51-53. 


ECONOMIC   WOODS    OF   THE    UNITED    STATES  69 


Wood  substance  itself,  being  insoluble  in  water  or  weak 
alkaline  solutions,  is  necessarily  tasteless.  The  characteristic 
taste  of  certain  woods  is  due  then  to  soluble  substances  deposited 
in  the  cell  lumina  or  infiltrated  into  the  cell  walls.  In  any  wood 
the  most  pronounced  flavor  is  obtained  from  the  sapwood;  it 
is  also  more  pronounced  in  green  material  than  in  dry.  This  is 
probably  due  to  the  fact  that  the  substances  giving  wood  its 
flavor  were  in  solution  or  soluble  form  in  the  living  sapwood. 
When  submerged  in  water  they  may  be  leached  out,  and  when 
exposed  to  air,  oxidized. 

Taste  is  occasionally  helpful  in  identifying  woods,  though, 
like  odor,  it  cannot  be  described  with  accuracy.  The  wood  of 
Libocedrus  decurrens  has  a  very  spicy  flavor;  that  of  Pinus  palus* 
tris  terebinthic;  that  of  Chamcecyparis  lawsoniana  spicy-resinous; 
that  of  Sassafras  rather  spicy.  The  wood  of  Castanea  has  no 
special  flavor,  but  on  account  of  the  tannin  in  it,  has  an  astringent 
effect  on  the  mouth. 


ADDITIONAL  REFERENCES 

Vessels  (pp.  14-16) 

Jeffrey,  Edward  C,  and  Cole,  Ruth  D.:  Experimental  In- 
vestigations on  the  Genus  Drimys.  Annals  of  Botany,  30:  359- 
368,  1916. 

Knight,  Margaret:  Drimys  Winteri  and  Drimys  odorata  (note). 
Annals  of  Botany,  29:  310-311,  1915. 

Thompson,  W.  P.,  and  Bailey,  I.  W.:  Are  Tetracentron,  Trocho- 
dendron,  and  Drimys  Specialized  or  Primitive  Types  ?  Memoirs 
of  the  N.  Y.  Bot.  Garden,  6:  27-32.     Aug.  31,  1916. 


Tracheids  (pp.  16-18) 

Gerry,  Eloise:  A  comparison  of  Tracheid  Dimensions  in  Long- 
leaf  Pine  and  Douglas  Fir,  with  Data  on  the  Strength  and 
Length,  Mean  Diameter  and  Thickness  of  Wall  of  the  Tracheids. 
Science,  43:  1106  :  360,  1916. 


70  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

Gerry,  Eloise:  Fiber  Measurement  Studies:  Length  Variations, 
Where  they  Occur  and  their  Relation  to  the  Strength  and  Uses 
of  Wood.     Science,  41:  1048  :  179,  1915. 

Groom,  Percy:  A  Preliminary  Inquiry  into  the  Significance  of 
Tracheid-Caliber  in  Coniferse.  Bot.  Gaz.,  57:4:287-307, 
Apr.  1914. 

Lee,  H.  N.,  and  Smith,  E.  M.:  Douglas  Fir  Fiber,  With  Special 
Reference  to  Length.     For.  Quarterly,  Dec.  1916. 

Mell,  D.  C.:  Length  of  Tracheids  in  Coniferous  Wood.  Paper 
Trade  Journal,  New  York,  June  15,  1911,  p.  52. 

Record,  Samuel  J.:  The  Significance  of  Resinous  Tracheids,  Bot. 
Gaz.,  66:  1:61-67,  July  1918. 

Sanio,  Karl:  Ueber  die  Grosse  der  Holzzellen  bei  der  Gemeinen 
Kiefer   (Pinus  silvestris  L.).     Jahrb.   Wiss.   Bot.,   8:401-420, 

1872. 

Sanio,  Karl:  Anatomie  der  gemeinen  Kiefer  (Pinus  silvestris  L.) 
II.   Jahrb.  Wiss.  Bot.,  9  :  50-126. 

Shepard,  H.  B.,  and  Bailey,  I.  W.:  Some  Observations  on  the 
Variation  in  Length  of  Coniferous  Fibers.  Proc.  Soc.  Am.  For., 
9:4:522-527,  Oct.  1914. 

Wood  Parenchyma  (pp.  21-23) 

Krah,  F.  W. :  Ueber  die  Vertheilung  der  parenchymatischen 
Elemente  im  Xylem  und  Phloem  der  Dicotylen  Laubbaume. 
Berlin,  1883. 

Rays  (pp.  23-29) 

Chrysler,  M.  A.:  The  Medullary  Rays  of  Cedrus.  Bot.  Gaz., 
59:5:387-396,  May  1915. 

Holden,  Ruth:  Ray  Tracheids  in  the  Coniferales.  Bot.  Gaz., 
55:  1:  56-65,  1913. 

Langdon,  LaDema  M.:  The  Ray  System  of  Quercus  alba.  Bot. 
Gaz.,  65:  4:  313-323,  Apr.  1918. 

Thompson,  W.  P.:  Ray  Tracheids  in  Abies.  Bot.  Gaz., 
53:4:331-338,  Apr.  1912. 

Resin  Ducts  (pp.  29-31) 

Record,  Samuel  J.:  Intercellular  Canals  in  Dicotyledonous 
Woods,  Journ.  Forestry,  16:  4:  429-441,  Apr.  1918. 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  71 

Pits  (pp.  31-35) 

Bailey,  Irving  W.:  The  Preservative  Treatment  of  Wood.  II. 
The  Structure  of  the  Pit  Membranes  in  the  Tracheids  of  Conifers 
and  their  Relation  to  the  Penetration  of  Gases,  Liquids,  and 
Finely  Divided  Solids  into  Green  and  Seasoned  Wood.  For. 
Quarterly,  11:  1:  12-20,  Mch.  1913. 

Bailey,  Irving  W. :  The  Structure  of  the  Bordered  Pits  of  Conifers 
and  Its  Bearing  upon  the  Tension  Hypothesis  of  the  Ascent  of 
Sap  in  Plants.     Bot.  Gaz.,  62:  2:  133-142,  Aug.  1916. 

Brown,  Forest  B.  H.:  Variation  in  the  Size  of  Ray  Pits  of  Coni- 
fers.    Ohio  Naturalist,  15:  542-550,  June  1915. 

Tyloses  (pp.  35-36) 

Gerry,  Eloise:  Tyloses:  Their  Occurrence  and  Practical  Signif- 
icance in  Some  American  Woods.  Journ.  Agr.  Research, 
1:6:445-470,  1914. 

Pith  Flecks  (pp.  36-37) 

Brown,  H.  P.:  Pith-ray  Flecks  in  Wood.  Cir.  25,  U.  S.  Forest 
Service,  Washington,  D.  C,  1913. 

Greene,  Chas.  T. :  The  Cambium  Miner  in  River  Birch.  Journ. 
Agr.  Research,  1:6:  471-4,  1914. 

Nielsen,  J.  C:  Zoologische  Studien  iiber  die  Markflecke.  Zool. 
Jahrb.,  Abt.  System,  Geoiigr.  w.  Biol.  Trere,  23:  6:  725-738, 
1906. 

Density  and  Weight  (pp.  49-52) 

Dunlap,  Frederick  :  Density  of  Wood  Substance  and  Porosity  of 
Wood.     Journ.  Agr.  Research,  2:6:  423-428,  Sept.  1914. 

Gaskill,  Alfred:  Specific  Gravity  and  Weight  of  the  Most  Im- 
portant American  Woods:  A  Study  and  Compilation.  For. 
Quarterly,  11:  4:  527-530,  Dec.  1913. 

Record,  Samuel  J. :  The  Mechanical  Properties  of  Wood.  New 
York,  John  Wiley  &  Sons,  Inc.,  1914,  pp.  54-58. 

Permeability  (pp.  60-62) 

Teesdale,  Clyde  H.:  Relative  Resistance  of  Various  Conifers  to 
Injection  with  Creosote.  Bui.  101,  U.  S.  Dept.  Agr.,  Wash- 
ington, D.  C,  1914. 


72  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

Teesdale,  Clyde  H.,  and  MacLean,  J.  D.:  Relative  Resistance 
of  Various  Hardwoods  to  Injection  with  Creosote.  Bui.  606, 
U.  S.  Dept.  Agr.,  Washington,  D.  C,  1918. 

Conductivi'y  (p.  62) 

Hiruma,  Jujiro:  Experiment  of  the  Electric  Resistance  in  Wood. 
Extracts  from  the  Bulletin  of  the  Forest  Experiment  Station, 
Meguro,  Tokyo.  Pub.  by  Bur.  of  For.,  Tokyo,  Japan,  1915,  pp. 
59-65. 


PART  II 

KEY    TO    THE   ECONOMIC    WOODS   OF    THE 
UNITED   STATES 

EXPLANATORY    NOTES 

The  descriptive  key  given  in  the  following  pages  is  based  upon 
features  visible  with  the  unaided  eye  and  with  a  small  hand  lens, 
and  also  upon  features  visible  only  under  the  compound  micro- 
scope.    The  latter  are  indicated  by  smaller  type. 

The  small  numerals  following  the  names  of  the  woods  refer  to 
a  list  of  references  on  pp.  109-117. 

The  capitals  in  parentheses  following  the  specific  names  refer 
to  the  regions  indicated  on  the  map  (Plate  I,  Natural  Forest 
Regions  of  the  United  States)  and  indicate  in  a  general  way  the 
natural  distribution  of  the  species: 

(P),  Pacific  Coast  Forest;  (R),  Rocky  Mountain  Forest;  (N), 
Northern  Forest;  (C),  Central  Hardwood  Forest;  (S),  Southern 
Forest;  (T),  Tropical  or  Sub-tropical  Forest;  (n),  north;  (s),  south; 
(Int.),  Introduced  into  the  United  States.  Where  more  than  one 
region  is  indicated  the  more  important  is  placed  first. 


I.   Non-porous  Woods:  Gymnosperms,  Conifers,  Soft- 
woods.    (For  II,  see  p.  85.) 

Vessels  absent.  Woods  comparatively  homogeneous;  com- 
posed mostly  of  tracheids  fairly  uniform  in  structure  and  arranged 
in  definite  radial  rows;  barely  visible  under  lens.  Growth  rings 
usually  quite  distinct  on  account  of  the  abrupt  change  in  density 
and  in  color  between  the  late  wood  of  one  year's  growth  and  the 
early  wood  of  the  next  (see  p.  40).  Wood  parenchyma  (resin 
cells)  and  resin  ducts  present  or  absent.  Rays  very  fine,  scarcely 
visible  without  a  lens.  Woods  with  or  without  pronounced 
resinous  odor  and  taste. 

73 


74  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

A  Resin  ducts,  both  vertical  and  horizontal  (fusiform  rays), 
present;  scattered  *;  the  vertical  appearing  on  longitudinal 
surface  as  fine  lines  or  scratches,  light  or  dark  in  color.  Rays 
with  tracheids.     (For  B,  see  p.  80.) 

a  Resin  ducts  plainly  visible  without  lens;  numerous  to 
moderately  so,  and  fairly  well  distributed.     (For  b,  see  p. 

78.) 

a1  Tracheids  normally  without  spirals.  Resin  ducts  not  constricted 
but  often  closed  with  tylosal  outgrowths  of  the  epithelial  cells; 
the  latter  are  thin-walled  and  normally  flattened.  Wood  paren- 
chyma only  in  association  with  resin  ducts,  not  isolated  or  zonate. 
Ray  tracheids  comparatively  large  and  numerous,  in  one  to  sev- 
eral marginal  rows  and  frequently  interspersed  in  high  rays  and 
often  entirely  composing  low  rays.  Woods  with  character- 
istic but  not  always  pronounced  resinous  odor.  Color 
contrast  between  heartwood  and  sapwood  usually  sharp 
and  distinct.     (For  b1,  see  p.  77.)  Pine.1 

a2  Moderate  contrast  in  color  and  density  between 
seasonal  growths;  transition  between  the  two  por- 
tions of  growth  ring  gradual;  texture  uniform. 
Woods  soft  to  medium,  comparatively  non-resinous. 
Color  pale  straw  to  reddish-brown.  Ray  tracheids 
with  upper  and  lower  walls  uniformly  thickened  or  smooth 
(Figs.  4,  5,  pp.  25-26).      Pits  present  in  the  tangential  walls 

of  the  late  wood.  Soft  Pine  Group. 

a3  Woods  soft,  straight-grained.  Ray  parenchyma  cells 
in  early  wood  with  1  or  2  large  simple  pits  in  each  cross- 
field,  f      (Fig.  4,  p.  25.) 

White  or  Five-leaved  Pine  Group. J2 


*  As  a  result  of  injury,  compact  peripheral  rows  of  ducts  may  arise  as  in 
the  case  of  certain  woods  in  which  resin  ducts  do  not  occur  normally. 

f  By  "cross-field"  is  meant  the  area  of  intersection  of  a  ray  cell  and  a  wood 
tracheid.  The  typical  condition  of  pitting  is  found  only  in  the  early  wood  as 
the  pits  may  be  semi-bordered  in  the  summer  wood. 

J  The  other  members  of  this  group  (a3)  are  P.  flexilis  James  (P),  P.  albi- 
caulis  Eng.  (R,  P),  and  P.  strobiformis  Eng.  (R).  Their  woods  are  of  no  com- 
mercial importance.  That  of  P.  albicaulis  is  characterized  by  resinous  tra- 
cheids. See  author's  "Significance  of  Resinous  Tracheids,"  Botanical  Gazette, 
66:1:61-67  (July,  1918). 


ECONOMIC   WOODS    OF   THE    UNITED    STATES  75 

a4  Color  varying  from  light  straw  or  creamy-white 
to  reddish-brown,  more  pronounced  in  summer 
wood  and  deepening  upon  exposure  to  sunlight. 
Texture  comparatively  fine.  Lustre  silky.. 
Wood  readily  cleavable  into  long  thin  strips. 
Resin  ducts  fairly  conspicuous,  especially  in 
second-growth,  appearing  on  longitudinal  sur- 
face as  straw-colored  or  light-brown  lines.  No 
sugary  exudations.  Sp.  gr.  .35-.43.  (Eastern) 
White  Pine,  Northern  Pine,  Pinus  strobus  L. 
(N)3;  Western  or  Idaho  White  Pine,  P.  monti- 
cola  Dougl.  (P). 

b4  Color  yellowish-white  to  very  light  brown,  never 
deeply  reddish;  brown  stain  common.  Texture 
coarse.  Lustre  dull.  Wood  not  readily 
cleavable  into  long  thin  strips.  Resin  ducts  con- 
spicuous and  usually  dark-colored.  Sugary 
exudations  and  sugar  pockets  common  on  fresh 
lumber.  Sp.  gr.  .32-40.  Sugar  Pine,  P.  lam- 
bertiana  Dougl.  (P).4 

b3  Wood  rather  hard,  cross-grained,  fine-textured. 
Color  yellowish,  uneven,  not  very  distinct  from 
sapwood.  Odor  often  like  beeswax.  Sp.  gr.  .45- 
.67.  Ray  parenchyma  cells  with  3-6  small  piciform  *  pits 
in  each  cross-field.      (Fig.  5,  p.  26.) 

Foxtail  and  Nut  Pine  Group. 
Pinon  pine,  P.  edulis  Eng.  (R).|5 

b2  Decided  contrast  in  density  and  usually  in  color  be- 
tween seasonal  growths;  transition  between  the  two 
portions  of  a  growth  ring  usually  abrupt;  texture 
variable,  often  very  uneven.  Woods  varying  from 
very  hard  to  soft;  moderately  to  highly  resinous. 
Color  variable,  but  mostly  darker  than  in  soft  pines. 
Ray  tracheids,  which  often  predominate  in  ray,  with  upper  and 

*  Pit  with  lenticular  opening  and  small  circular  border  as  in  rays  of  Picea. 

t  Microscopic  structures  for  this  group  apply  also  to  P.  quadrifolia  Pari. 
(P),  P.  cembroides  Zucc.  (R),  P.  monophylla  T.  &  F.  (R),  P.  balfouriana  Murr. 
(P),  P.  arislata  Eng.  (P).     These  woods  are  not  of  commercial  importance. 


76  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

lower  walls  irregularly  thickened,  dentate  to  reticulate  *  (Figs. 
6,  7,  pp.  27-28).  Pits  rarely  present  in  tangential  walls  of 
the  late  wood.  Pitch  Pine  Group. 

a3  Ray  parenchyma  cells  in  early  wood  with  1  or  2  large  simple 
pits  in  each  cross-field  (Fig.  6,  p.  27).  Wood  rather 
light  and  soft,  variable,  fairly  strong,  medium- 
textured,  not  highly  resinous.  Sp.  gr.  .42-.54. 
Red  Pine  Group.j  Red  or  Norway  Pine,  P.  resi- 
nosa  Ait.  (L).6 

b3  Ray  parenchyma  cells  in  early  wood  with  3-6  (occasionally 
more)  small,  irregular,  simple  (rarely  semi-bordered)  pits  in 

each  cross-field  (Fig.  7,  p.  28).     Yellow  Pine  Group. 

a4  Woods  variable  from  light  and  soft  to  moder- 
ately heavy  and  hard.  Western  Pines. 

a5  Wood  fairly  uniform,  soft,  not  highly  resin- 
ous, light-colored.  Sp.  gr.  .35-.47.  Tangen- 
tial surface  showing  conspicuous  "  pebbly  "  or 
"  dimpled  "  grain.  Lodgepole  Pine,  P.  con- 
torta  Loud.,  or  P.  murrayana  "O.C."  (R,  P).7 

b5  Wood  variable  from  light,  soft,  non-resinous, 
and  nearly  white  to  fairly  heavy,  hard,  res- 
inous, and  reddish-brown  in  color.  Sp.  gr. 
.39-. 60.  "  Pebbly  "  grain  not  characteristic 
though  occasionally  present.  Western  Yel- 
low Pine,  Western  Pine,  California,  New 
Mexico  or  Arizona  White  Pine,  Western  Soft 
Pine,  Bull  Pine,  P.  ponderosa  Laws.|     (R,  P;.8 

*  The  very  irregular  thickenings  of  the  upper  and  lower  walls  of  the  ray 
tracheids  are  peculiar  to  the  pitch  pines.  Spiral  markings  and  other  irregu- 
larities of  the  wall  found  occasionally  in  the  ray  tracheids  of  certain  other 
conifers  are  quite  distinct  from  the  heavy  sculpturing  in  the  ray  tracheids  of 
the  pitch  pines. 

t  The  microscopic  structure  of  P.  rcsinosa  characterizes  also  one  Asiatic 
and  two  European  pines  which  are  being  planted  to  some  extent  in  the  United 
States,  namely,  Japanese  Red  Pine,  P.  densiftora  S.  &  Z.,  Scotch  Pine,  P. 
sylvestris  L.,  and  Austrian  Pine,  P.  laricio  Poir. 

J  Included  under  this  name  are  closely  related  forms  whose  woods  are  not 
distinguishable.  The  softest  grades  of  the  wood  are  from  the  outer  portions 
of  large,  ovc -mature  timber. 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  77 

b4  Woods  varying  from  moderately  to  extremely 
heavy  and  hard.  Southern  Pines.*9 

a5  Woods  usually  very  dense  and  resinous,  with 
large  proportion  of  sharply  defined  late  wood. 
a6  Growth  rings  mostly  wide,  variable.     Sap- 
wood  thick.     Sp.  gr.   .50-.90,   usually  be- 
tween .65  and  .75.     Slash  or  Cuban  Pine, 
P.    caribaea   Mor.,    P.    heterophylla    (Ell.) 
Sudw.,  or  P.  cubensis  Gris.  (S).10 
b6  Growth  rings  mostly  narrow  beyond  first  2 
or  3  inches  of  radius,  fairly  uniform.     Sap- 
wood   thin.     Sp.   gr.    .50-.90,    usually   be- 
tween .60  and  .70.  Longleaf  Pine,  Georgia 
Pine,    P.    palustris   Mill.,    or    P.    australis 
Michx.  f.  (S).11 
b5  Woods  usually  moderately  dense  and  resinous, 
widely  variable;  medium  to  small  proportion 
of  late  wood  not  always  sharply  defined. 
a6  Growth  rings  variable,  narrow  to  extremely 
broad.     Sapwood   thick.     Sp.   gr.    .40-.80, 
usually  between  .45  and  .55.     Loblolly  or 
North  Carolina  Pine,  P.  taeda  L.  (S).12 
b6  Growth  rings  fairly  regular,  broad  toward 
pith  and  narrow  beyond  5-7  inches.     Sap- 
wood  rather  thick.     Sp.  gr.  .40-80,  usually 
between  .45  and  .55.     Shortleaf  Pine,  P. 
echinata  Mill.,  or  P.  mitis  Michx.  (S).13 
b1   Tracheids  normally  with  spirals. f     Resin  ducts  widely  variable  in 
size  and  arranged  often  in  short  tangential  groups;  ducts  con- 

*  Specific  identification  of  the  southern  pines  is  very  uncertain.  Since  the 
mechanical  and  physical  properties  of  the  woods  are  factors  of  the  density, 
classification  for  commercial  purposes  is  made  on  that  basis. 

t  The  spirals  in  the  tracheids  serve  to  distinguish  the  wood  of  Pseudotsuga 
from  that  of  all  others  resembling  it.  The  tracheids  of  Taxus  and  Tumion 
are  spiralled  but  the  woods  are  wholly  devoid  of  wood  parenchyma,  resin 
ducts,  and  ray  tracheids.  The  sporadic  occurrence  of  true  spirals  in  Picea, 
Larix  and  Pinus  has  been  noted  and  in  the  rare  instances  where  such  is  the 
case  the  other  anatomical  features  must  be  taken  into  account.  Spirals, 
which  are  thickenings  upon  the  inside  of  the  secondary  wall,  must  not  be  con- 
fused with  striations  which  are  slits  or  cracks  running  spirally  in  the  thick 
walls  of  the  late  wood  and  of  "  compression  wood  "  (rotholz)  of  many  conifers. 


78  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

stricted  at  intervals  but  rarely  closed  by  tylosal  outgrowths  of 
the  epithelial  cells;  the   latter   are   usually   small,  thick-walled, 
rounded.     Isolated  wood  parenchyma  strands  (resin  cells)  occa- 
sionally found.     Ray  tracheids  small,  usually  in  single  marginal 
rows,  sometimes  showing  minute  spirals.     Ray  parenchyma  pits 
small  and  more  or  less  piciform.      Wood  resembles  that  of 
Southern  Pines  but  for  the  most  part  is  without  very- 
pronounced  resinous  odor,  usually  less  pitchy,  and  on 
radial  surface  usually  shows  less  distinct  color  con- 
trast between   seasonal  growths.     Color  contrast  be- 
tween heartwood  and  sapwood  distinct.     Sp.  gr.  .39- 
.68,  mostly  between  .45  and  .55.     Growth  rings  more 
or  less  undulating,  showing  on  both  cross  and  longitu- 
dinal surfaces.     Wood  of  two  general  classes :  (^Fine- 
grained, fairly  uniform-textured,  moderately  light  and 
soft,  easy  to  work;  color    pale  reddish-yellow;  hence 
the  local  name  of  "  yellow  fir."     (2)  Coarse-grained, 
uneven-textured ;  early  wood  open  and  weak,  late  wood 
dense  and  flinty;  color  rather  deep  red,  hence  the  local 
name  of    "red   fir."     Douglas   Fir,  Spruce    or   Pine, 
Oregon  Pine,  Pseudotsuga  taxifolia  Brit.,  P.  douglasii 
Carr.,  or  P.  mucronata  (Raf.)  Sudw.     (P,  R).14 
b  Resin  ducts  mostly  small,  inconspicuous,  widely  scattered 
or  in  small  tangential  groups;  appearing  in  late  wood  com- 
monly as  small  whitish  dots;  usually  open;  epithelial  cells  small, 
normally  thick-walled,  rounded.     Isolated  wood  parenchyma  strands 
(resin  cells)  rare;  terminal.    Tracheids  rarely  with  spirals.    Ray  tra- 
cheids small,  usually  in  single  marginal  rows,  rarely  with  spirals.     Ray 
parenchyma  cells  thick-walled,  abundantly  pitted  in  upper,  lower 
and  end  walls;  pits  on  lateral  walls  lenticular  or  slit-like,  small,  semi- 
bordered,  2-6  in  each  cross-field  in  early  wood.* 
a1  Wood  variable,  but  mostly  hard  and  heavy,  with  de- 
decided  contrast  between  seasonal  growths;  sometimes 
decidedly  pitchy.     Sapwood  thin  with  distinct  line  of 
demarcation.  Larch.15 

*  The  woods  of  larch  and  spruce  bear  considerable  resemblance  microscopi- 
cally to  the  woods  of  the  foxtail  and  nut  pine  group.  They  can  usually  be 
readily  distinguished  by  the  nature  of  the  epithelial  cells  of  the  resin  ducts, 
being  thin-walled  and  flattened  in  the  pines  and,  with  occasional  exceptions, 
thick-walled  and  rounded  in  the  others.  This  is  seen  to  best  advantage  in  the 
fusiform  rays  (tangential  section). 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  79 

a2  Color     yellowish-brown,     not     reddish.       Texture 
medium.     Wood  usually  in  small  sizes,  not  straight- 
grained,  not  highly  resinous.     Sp.  gr.  .54-.78,  mostly 
between  .55  and  .65.     Larch,  Tamarack,  Hackma- 
tack, Larix  laricina  (Du  Roi)  Koch.,  or  L.  americana 
Michx.  (N). 
b2  Color  red   to  reddish-brown.     Texture   coarse  and 
harsh.     Wood   obtainable   in   large   sizes,    straight- 
grained,  sometimes  extremely  dense  and  very  pitchy. 
Sp.  gr.  .59-83,  mostly  between  .60  and  .70.    Western 
Larch,  Tamarack,  L.  occidentalis  Nutt.  (R). 
b1  Wood  varying  from  very  light  and  soft  to  moderately 
so,    with    from    slight    to    decided    contrast    between 
seasonal  growths;  non-resinous.     Texture  fine.     Lustre 
satiny  and  finely  dappled,  especially  on  tangential  sur- 
face.    Sapwood  usually  without  distinct  line  of  demar- 
cation. Spruce.16 
a2  Color  white  or  very  light,  uniform,  with  little  or  no 
contrast  between  heartwood  and  sapwood.     Resin 
ducts  scarcely  visible  without  lens.     Sp.  gr.  .31-.53, 
mostly  between  .35  and  .45. 

a3  Grain  varying  from  extremely  fine  to  medium.* 
Red  Spruce,  Picea  rubens  Sarg.,  or  P.  rubra  Diet. 
(N)17;     Black    Spruce,   P.  mariana  Mill.,   or   P. 
nigra  Link.  (N). 
b3  Grain  mostly  coarse.     White  or  Cat  Spruce,  P. 
canadensis  (Mill.)  B.  S.  P.,  or  P.  alba  Link.  (N)t; 
Engelmann  Spruce,  P.  engelmanni  Eng.  (R). 
b2  Color  reddish  or  pinkish,  fading  gradually    outward 
into    sapwood;    deepest    in    rays.     Texture    rather 
wooly.     Resin  ducts  fairly  distinct.     Sp.  gr.  .34-.65, 
mostly    between    .35    and    .40.     Sitka    Spruce,    P. 
sitchensis  (Bong.)  T.  &  M.  (Pn). 

*  Since  fineness  of  grain  (i.e.,  width  of  growth  rings)  is  largely  determined 
by  external  factors  it  is  an  unreliable  diagnostic  feature  and  is  resorted  to  here 
because  constant  features  of  distinction  are  apparently  wanting  and  also  be- 
cause it  is  used  to  some  extent  by  lumbermen. 

t  The  wood  of  the  eastern  spruces,  particularly  P.  canadensis,  rather 
closely  resembles  that  of  the  balsam  fir,  and  the  two  are  often  associated  both 
in  the  forest  and  in  the  market.  The  peculiar  dappled  lustre  of  spruce  and 
the  presence  of  resin  ducts  and  ray  tracheids  are  distinctive. 


80  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

B  Vertical  resin  ducts  normally  absent;  may  be  present  as  result 
of  injury  in  which  event  they  are  arranged  in  a  compact 
peripheral  row  (Fig.  10,  p.  32) ;  horizontal  resin  ducts  (fusiform  rays) 
absent.*     Ray  tracheids  present  or  absent. t 

a  Tracheids  without  spirals.      (For  b,  see  p.  85.) 

a1  Woods  without  aromatic  odor.  (For  b1,  see  p.  82.) 
a2  Resin  cells  absent  or  few;  never  visible  without 
compound  microscope.  Color  of  woods  not  pro- 
nounced, though  late  wood  exhibits  a  slight  purplish 
tinge.  Without  sharp  demarcation  and  with  little 
color  contrast  between  heartwood  and  sapwood. 
a3  Ray  tracheids  normally  absent.  Fir.ls 

a4  Color  white  or  pale  brown  in  general  appearance, 
with  late  wood  rather  purplish.     Wood  often 
coarse-grained,  soft  and  weak.     Sp.  gr.  .29-.45, 
mostly  between  .35  and  .40.     Balsam  or  Balsam 
Fir,  Abies  balsamea  Mill.  (N);  Lowland  Fir,  A. 
grandis  Lindl.  (P) ;  White  Firs,  A.  concolor  Parry 
(P)  and  A.  amabilis  Forb.  (P). 
b4  Color  yellowish-brown  with  reddish  tinge;  rays 
decidedly   reddish.     Wood   moderately   to   de- 
cidedly   heavy    and    hard.     Sp.    gr.     .41-.58. 
Noble  Fir,  A.  nobilis  Lindl.  (P);  Red  Fir,  A. 
magnified  Murr.  (P). 
b3  Ray  tracheids  present  in  single  marginal  rows  and  some- 
times interspersed.  Hemlock.19 
a4  Odor  disagreeable,  though  not  very  pronounced 
in    small    dry    specimens.       Wood    harsh    and 
slivery,  inclined  to  split  apart  at  growth  rings; 

*  Traumatic  resin  ducts  occur  occasionally  in  the  woods  of  various  species 
of  Abies,  of  Tsuga  heterophylla,  both  species  of  Sequoia,  and  certain  species  of 
Cedrus,  but  in  no  other  genera  of  this  group.  Traumatic  horizontal  canals 
have  been  reported  only  for  certain  species  of  Cedrus  and  some  extinct  species 
of  Sequoia  (?)  not  included  in  this  key. 

t  Small  marginal  ray  tracheids  are  characteristic  of  Tsuga.  No  ray  tra- 
cheids have  been  observed  in  Taxodium,  Tumion  (Torreya),  and  Taxus. 
Their  more  or  less  sporadic  occurrence  in  Abies,  Sequoia,  Chammcyparis, 
Thuya,  Juniperus,  and  (very  rarely)  Libocedrus  has  been  noted  by  the  author 
or  reported  by  others.  (See  W.  P.  Thompson,  "Ray  tracheids  in  Abies,"  Bot. 
Gaz.,  53.4:  331-338;  also  Ruth  Holden,  "Ray  tracheids  in  the  Coniferales," 
Bot.  Gaz.,  55:  1:  56-65). 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  81 

brittle.     Sp.  gr.  .33-.52,  mostly  between  .40  and 
.45.     Contrast  between  seasonal  growths  very- 
pronounced;    transition    abrupt.     Color    light 
buff  with  reddish-brown  tinge.     No  resin  ducts 
or  aggregates  of  resinous  tracheids.     (Eastern) 
Hemlock,  Tsuga  canadensis  Carr.  (N). 
b4  Odorless  when  dry;  green  wood  slightly  sour- 
smelling.     Wood  of  rather  uniform  texture,  not 
particularly     harsh     and     splintery,     straight- 
grained  and  fairly  easy  to  work.    Sp.  gr.  .30-.57, 
mostly  between  .40  and  .50.     Transition  from 
early  wood  to  late  wood  rather  gradual.     Color 
light,    sometimes    pinkish     or    reddish-brown. 
Small   black    checks   common.     Aggregates   of 
resinous  tracheids,  somewhat  resembling  resin 
ducts  on  cross  section,  fairly  common;   wound 
ducts  in  peripheral  rows  occasionally  present. 
Western  Hemlock,  T.  heterophylla  Sarg.  (P).20 
b2  Resin  cells  numerous,  visible  under  hand  lens   and 
often  collectively  to  unaided  eye,  particularly  in  sap- 
wood;  frequently  zonate.      Color  of  woods  charac- 
teristic.    Distinct  demarcation  between  heartwood 
and  sapwood. 

a3  Color  varying  from  light  cherry-red  to  purplish. 
Texture  rather  coarse.  Woods  without  odor  or 
taste.  Wound  ducts  sometimes  present  in  periph- 
eral rows.  Resin  masses  in  wood  parenchyma 
strands  appear  under  lens  on  longitudinal  surface 
as  rows  of  black  or  amber  beads.  Rays  biseriate  in 
part;  occasionally  with  marginal  or  isolated  ray  tracheids; 
lateral  pits  in  ray  parenchyma  cells  large  and,  in  early 
wood,  horizontally  elongated;  no  terminal  pits.  Bordered 
pits  in  tracheids  of  early  wood  commonly  paired. 

Sequoias.21 
a4  Wood  deeply  colored,  purplish  or  maroon. 
Growth  rings  usually  very  narrow.  Texture 
uniform.  Wood  weak,  brittle,  and  soft.  Sp. 
gr.  .25-.33.  Bigtree,  Giant  Sequoia,  Sequoia 
washingtoniana  (Winsl.)  Sudw.,  or  S.  gigantea 
Dec.  (P).22 


82  ECONOMIC    WOODS   OF   THE   UNITED    STATES 

b4  Wood  less  deeply  colored,  mostly  light  cherry- 
red.     Considerable  variation  in  width  of  growth 
rings.     Wood  variable  from  light,  soft  and  uni- 
form-textured to  fairly  heavy,  hard,  and  show- 
ing decided  contrast  between  the  two  portions 
of  a  growth  ring.     Resin  masses  more  prominent 
than  in  preceding.     Sp.  gr.  .40-.52,  mostly  be- 
tween .40  and  .45.     Redwood,  S.  sempervirens 
(Lamb.)  Endl.  (P).23 
b3  Color  widely  variable,  yellowish,  reddish,  brown, 
variegated,     or    almost    black.       Texture     fine. 
Smooth  surface  of  denser  specimens  usually  looks 
and  feels  greasy  or  waxy,  sometimes  as  though 
heavily  impregnated  with  paramne.     Odor  some- 
what rancid  or  wanting.     Wood  variable  from  very 
soft  and  light  to  rather  hard  and  heavy.     Sp.  gr. 
.34-.55,  mostly  between  .40  and  .50.     No  resin 
masses  visible  under  lens ;  under  compound  microscope 
resin  in  wood  parenchyma  strands  appears  mostly  in  globu- 
lar masses.     Rays  uniseriate,  without  tracheids;  lateral  pits 
in  ray  cells  large  and  obliquely  elongated;  no  terminal  pits. 
Bordered  pits  in  tracheids  of  spring  wood  rather  small  and 
often  irregularly  disposed  or,  near  ends,  arranged  in  pairs  or 
in  horizontal  rows  of  3  or  4.    Southern  or  Bald  Cypress,* 
Taxodium  distichum  Rich.  (S).24 
b1  Woods  with  aromatic  odor.  Cedar  Group.25 

a2  Color  light  clear  yellow  or  slightly  brownish,  without 
much  distinction  between  heartwood  and  sapwood. 
Late  wood  inconspicuous.  Odor  pronounced;  pun- 
gent. Taste  unpleasantly  spicy-resinous.  Woods 
varying  from  light  and  soft  to  moderately  so.  Tex- 
ture fine,  uniform.     Sp.  gr.  .40-. 54,  average  about  .45. 

Yellow  Cedars. 

*  A  varietal  form,  T.  distichum  var.  imbricarium  Sarg.,  is  recognized  by 
botanists  but  the  wood  is  scarcely  if  at  all  distinguishable  from  the  specific 
form.  Lumbermen  refer  to  different  grades  of  wood  as  yellow,  red,  white,  or 
black,  sometimes  in  connection  with  the  color,  sometimes  in  reference  to 
buoyancy  of  the  logs.  Cypress  lumber  is  often  "pecky"  or  "peggy,"  that  is, 
filled  with  large  fungous-galleries.  The  wood  of  the  "knees"  is  extremely 
light,  soft,  and  uniform-textured  and  is  used  commercially  for  floats.  The 
tracheid  walls  are  very  thin,  the  cavities  large,  and  the  radial  pits  are  con- 
siderably smaller  than  those  in  stem  wood. 


ECONOMIC   WOODS   OF    THE    UNITED    STATES  83 

a3  Color  very  light.  Texture  very  fine.  Odor  rather 
mild;  unpleasant.  Ray  tracheids  common  in  low  rays. 
Yellow  Cedar,  Yellow  or  Sitka  Cypress,  Chamcecy- 
paris  nootkatensis  Spach.  (P). 

b3  Color  deep  yellow,  sometimes  brownish.  Texture 
moderately  fine.  Odor  very  pungent.  Ray  tra- 
cheids rarely  present.  Port  Orford  Cedar,  Lawson's 
Cypress,  Oregon  Cedar,  C.  lawsoniana  Pari.  (P). 

b2  Color  varying  from  light  brown  to  purple,   never 
yellow.     Late    wood    distinct;    often    conspicuous. 
Odor  variable,   more  or  less  pronounced,   but  not 
pungent.     Taste  not  unpleasant. 
a3  Wood  firm  and  compact,  cutting  smoothly  across 
the  grain.     Moderate  contrast  between  seasonal 
growths;    transition    gradual.     Demarcation    be- 
tween heartwood  and  sapwood  usually  distinct. 
Red  Cedar  Group. 

a4  Color  pale  reddish-brown  or  roseate,  uniform; 
rays  brown.  Odor  pronounced.  Taste  spicy. 
Resin  cells  fairly  numerous,  zonate,  mostly  in 
late  wood;  usually  not  visible  with  lens.  Tex- 
ture rather  fine,  uniform.  Growth  rings  regu- 
lar; late  wood  fairly  conspicuous.  Heartwood 
often  "  pecky "  as  in  Taxodium.  Sp.  gr. 
.34-.4G,  mostly  between  .35  and  .40.  Rays  often 
gummy;  1-8,  mostly  3-5,  cells  high;  ray  tracheids  absent. 
Incense  Cedar,  Libocedrus  decurrens  Torr.  (P).26 

b4  Color  purple  or  deep  red,  soon  becoming  dull 
brown  upon  exposure  to  sunlight;  often  streaked 
with  white;  rays  deep  red  or  purple.  Odor  and 
taste  characteristic  but  mild;  not  sweetish  or 
spicy.  Resin  cells  very  numerous,  deeply  colored, 
mostly  zonate  (Plate  II,  Fig.  3)  in  concentric 
lines  visible  with  lens  and  often  without  it. 
Rays  gummy,  1-20  cells  high,  very  irregular. 
Texture  very  fine  and  uniform.  Growth  rings 
often  very  irregular  in  width  and  outline,  fre- 
quently eccentric;  summer  wood  not  conspic- 
uous,   sometimes   doubled    or    trebled.     Wood 


84  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

usually  knotty  except  in  very  small  sizes;  never 
"  pecky."  Sp.  gr.  .45-.53,  average  about  .49. 
Ray  tracheids  fairly  common  and  (1)  marginal,  in  which 
case  they  are  of  irregular  shape  or  upright,  or  (2)  con- 
stituting low  rays  entirely  or  in  alternation  with  ray 
parenchyma  cells.  Juniper,  Red  or  Pencil  Cedar, 
Juniperus  virginiana  L.  (N,  C);  Southern  Red 
Cedar,  J.  barbadensis  L.  (S).*27 

b3  Wood  soft  and  more  or  less  spongy. 

a4  Decided  contrast  between  seasonal  growths; 
late  wood  thin  but  hard,  early  wood  very  soft; 
transition  between  the  two  portions  of  a  growth 
ring  abrupt.  Sp.  gr.  .34-.42.  Color  varying 
from  various  shades  of  brown  to  decidedly  red- 
dish; often  streaked.  Resin  cells  inconspicuous, 
often  zonate  in  widely  separated  growth  rings. 
Bordered  pits  usually  in  pairs  near  ends  of  tracheids  in 

early  wood.  Western  Red  Cedar,  Giant  Ar- 
borvitae,  Canoe  Cedar,  Shingle  Cedar,  Thuya 
plicata  Don.,  or  T.  gigantea  Nutt.  (P).28 

b4  Moderate  contrast  between  seasonal  growths;, 
late  wood  rather  soft;  transition  between  the 
two  portions  of  a  growth  ring  gradual.  Color 
pale  brown  or  pinkish,  never  very  dark;  little 
contrast  between  heartwood  and  sapwood. 
Resin  cells  zonate  or  diffuse.  Bordered  pits  in 
tracheids  rarely  paired.  White  Cedar  Group. 

a5  Color  pale  brown;  intermingling  of  lighter  and 
darker  shades  common.  Resin  cells  rarely 
visible  with  lens.  Odor  very  mild.  Wood 
very  soft  and  rather  punky;  brash.  Growth 
rings  mostly  narrow.  Sp.  gr.  .28-.37,  average 
about  .32.  Arborvitae,  Northern  White  Cedar, 
T.  occidentalis  L.  (N). 

*  There  are  a  number  of  western  species  of  Juniperus  but  they  are  only  of 
local  importance.  Their  woods  resemble  the  eastern  species  but  are  mostly 
harder  and  heavier,  and  the  color  of  some  of  them  is  brown  rather  than  deep 
red  or  purple. 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  85 

b5  Color  light  reddish-brown  or  pinkish.  Con- 
centric lines  of  resin  cells  visible  with  lens  and 
often  without  it.  Odor  more  pronounced  and 
wood  firmer  and  less  brash  than  in  preceding. 
Growth  rings  mostly  moderately  wide.  Sp. 
gr.  .30-.45,  mostly  between  .30  and  .35. 
White  Cedar,  Chamcecy parts  thyoides  (L.) 
B.  S.  P.,  or  C.  sphceroidea  Spach.  (N,  S). 
b  Tracheids  with  spirals.  Wood  parenchyma  (resin  cells)  and  ray 
tracheids  wholly  absent.  Taxaceae.* 

a1  Color  reddish-brown  to  rose-red.  Clear  demarcation 
between  heartwood  and  sapwood.  Woods  without 
odor. 

a2  Color  bright  orange  to  rose-red;  thin  sapwood  pale 
yellow.  Wood  uniform  and  very  dense.  Sp.  gr. 
.62— .70.      Tracheids  very  small,  thick-walled. 

(Western)  Yew,  Taxus  brevifolia  Nutt.  (P). 

b2  Color   brownish-red;    thin   sapwood   nearly   white. 
Wood  somewhat  less  dense.     Sp.  gr.  .63.     Tracheids 
comparatively  large  and  not  so  thick-walled  as  in  preceding. 
Florida  Yew,  T.  floridana  Nutt.  (S). 

b1  Color  bright  clear  yellow,  without  pronounced  demar- 
cation between  heartwood  and  sapwood.  Wood  with 
characteristic  odor.  Sp.  gr.  .44-60,  mostly  around 
.50.  California  Nutmeg,  Tumion  californicum  (Torr.) 
Greene,  or  Torreya  californica  Torr.  (Ps);  Stinking 
Cedar,  Tumion  taxifnliutn  (Arn.)  Greene,  or  Torreya 
taxifolia  Arn.  (S). 

II.   Porous  Woods:  Dicotyledons,  Hardwoods,  Broad- 
leaf  Woods 

Vessels  present;  varying  in  size  from  large  and  conspicuous  to 
minute.  Woods  comparatively  heterogeneous,  being  composed 
of  several  kinds  of  elements,  mostly  irregularly  disposed.  Growth 
rings  varying  from  very  distinct  in  the  ring-porous  woods  to  in- 
distinct   in    some    of    the    diffuse-porous.     Wood    parenchyma 


*  The  woods  of  the  Taxacese  are  of  very  limited  commercial  importance 
because  of  their  scarcity  and  small  size. 


86  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

present  in  variable  amount;  often  conspicuous.  Resin  ducts 
absent.  Gum  ducts  sometimes  present  in  a  few  species.  Rays 
varying  from  minute  to  large  and  conspicuous. 

A  Rixg-porous  Woods.     Largest  pores  localized  in  a  distinct 
ring  or  band  in  early  wood.*     (For  B,  see  p.  95.) 

a  Late  wood  with  radial  lines  or  patches  (frequently 
branched  or  fan-like)  composed  of  small  pores  and  paren- 
chyma, usually  lighter  colored  than  remainder  of  wood; 
also  with  parenchyma  in  fine  concentric  lines,  distinct  to 
indistinct.!     (For  b,  see  p.  88.) 

a1  Rays  all  very  fine,  inconspicuous. t     Woods  soft  to 
moderately  hard;  stiff  but  not  strong;  sp.  gr.  .45-.59. 

a2  Pores  in  early  wood  few,  small,  nearly  circular,  open, 
and  rather  widely  separated  in  a  single  row.  Color 
of  wood  light  brown  or  roseate.  Odorless  and  taste- 
less. Vessels  without  spirals;  bordered  pits  circular,  tending 
to  become  scalariform  in  small  vessels;  perforations  simple  with 
tendency  to  scalariform  with  few  bars;  pits  into  ray  cells  either 
half-bordered  or  simple.  Rays  uniseriate  (occasionally  bise- 
riate  in  median  portion),  5-15  cells  high;  more  or  less  heteroge- 
neous. Western  Chinquapin,  Castanopsis  chrysophylla 
de  C.  (P). 

b2  Pores  in  early  wood  very  numerous,  large,  mostly 
oval  or  elliptical,  open,  and  in  a  broad  zone.  Color 
of  wood  brown;  stains  blue-black  in  contact  with 
iron  when  moist.  Odor  of  fresh  wood  mild  but  dis- 
tinct. Taste  somewhat  astringent  due  to  tannin 
content.  (Microscopic  features  given  in  preceding  apply 
here.)      Chestnut, §  Castanea  dentata  Borkh.  (C,  N).29 

*  This  feature  may  be  obscure  in  very  narrow  growth  rings  where  the  pro- 
portion of  late  wood  is  so  reduced  that  the  wood  appears  diffuse-porous. 

t  The  visibility  of  wood  parenchyma  is  usually  increased  by  moistening 
the  smoothly  cut  end  of  the  specimen. 

t  The  distinctness  of  the  rays  refers  to  the  cross  section  unless  otherwise 
stated. 

§  The  chinquapin  chestnut  (Castanea  pumila  Mill.)  is  a  small  southern  tree 
of  only  local  importance  for  fence  posts  and  fuel.  The  wood  is  mostly  harder, 
heavier  and  of  slower  growth  than  the  other  species.  The  structures  of  the 
two  woods  are  nearly  identical. 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  87 

b1  Rays  of  two  kinds:  (1)  large  and  conspicuous,*  showing 
as  broad  flakes  on  radial  surface  and  as  distinct  lines 
on  the  tangential;  (2)  very  fine  and  inconspicuous, 
mostly  invisible  without  lens.  (See  Plate  III,  Fig.  1.) 
Wood  hard  and  heavy;  usually  very  tough  and  strong; 
sp.  gr.  .65-90.  Odor  of  fresh  wood  characteristic. 
(Microscopic  features  given  above  also  apply  here,  except  as  to 
size  of  rays.)  Oak.f30 

a2  Pores  in  late  wood  individually  distinct  under  lens 
and  few  enough  to  be  readily  counted;  arranged 
mostly  in  fairly  definite  radial  rows  (except  in  nar- 
row growth  rings).  Pores  in  early  wood  usually 
crowded  in  a  broad  zone  and  becoming  gradually 
smaller  outward  (occasional  exceptions).  All  pores 
usually  open;  sometimes  partially  or  wholly  filled 
with  tyloses.  Ray  lines  on  tangential  surface  usually 
short  (rarely  exceeding  1  inch),  and  more  or  less  in- 
terrupted by  wood  fibers.  Color  of  wood  typically 
pale  reddish-brown,  deeper  near  knots.  Pores  in  late 
wood  are  thick-walled  and  more  or  less  circular  in  outline. 
(Plate  II,  Fig.  6.)  Black  and  Red  Oak  Group. 
Red  Oak,  Quercus  rubra  L.  (C,  N) ;  Black  or  Yellow 
Oak,  Q.  velutina  Lam.  (C,  N);  Spotted  Oak,  Q. 
texana  Buckl.  (C,  S) ;  Spanish  Oak  or  Southern  Red 
Oak,  Q.  digitata  Sudw.,  or  Q.  falcata  Michx.  (S,  C) ; 
Scarlet  Oak,  Q.  coccinea  Muench.  (C,  N) ;  Pin  Oak, 
Q.  palustris  Muench.  (C) ;  Black  Jack,  Q.  marilandica 
Muench.  (C,  S) ;  California  Black  Oak,  Q.  californica 
(Torr.)  Coop.  (P);  Water  Oak,  Q.  nigra  L.  (S,  C); 
Laurel  Oak,  Q.  laurifolia  Michx.  (S) ;  Shingle  Oak, 
Q.  imbricaria  Michx.  (C,  N) ;  Willow  Oak,  Q.  phellos 
L.  (S). 


*  Occasional  specimens  of  branches  or  of  rather  small  stems  are  found 
which  have  few  or  no  large  rays.  Oak  wood  is  quite  distinct,  however,  even 
when  this  prominent  feature  is  wanting. 

t  The  author  is  of  the  opinion  that  the  features  so  far  recognized  as  con- 
stant in  the  woods  of  the  oaks  will  permit  separation  into  general  groups  only. 
Fortunately,  this  classification  corresponds  very  closely  to  the  technical 
properties  of  the  woods  and  this  fact  renders  specific  distinctions  of  much  less 
importance. 


88  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

b2  Pores  in  late  wood  rarely  individually  distinct  under 
lens  and  not  few  enough  to  be  readily  counted;  ar- 
ranged in  fan-shaped  patches  often  joined  tangen- 
tially  in  outer  portion.     Pores  in  early  wood  in  few 
(1-3)  rows,  usually  not  crowded;  transition  to  small 
pores  of  summer  wood  abrupt;*   usually  closed  with 
tyloses   except   in   outer   sapwood.f     Ray   lines   on 
tangential  surface  often  quite  long  (up  to  5  inches) 
narrow,  and  straight.     Color  of  wood  pale  to  medium 
dark  brown;  not  reddish. J     Pores  in  late  wood  are  thin- 
walled    and    angular    in    outline.       White    Oak    Group. § 
White  Oak,  Quercus  alba  L.  (C,  N)  (Frontispiece)31; 
Bur  Oak,  Q.  macrocarpa  Michx.  (C,  N)  (Figs.  13,  14, 
p.  42);  Overcup  Oak,  Q.  lyrata  Walt.  (C,  S);  Post 
Oak,  Q.  minor  Sarg.,  or  Q.  stellata  Wang.  (C,  A,  S); 
Oregon  Oak,  Q.  garryana  Dougl.  (P);  Chestnut  or 
Rock  Oak,  Q.  prinus  L   (N,   C)32;   Chinquapin  or 
Yellow  Chestnut  Oak,  Q.  acuminata  (Michx.)  Houba, 
or  Q.  muhlenbergii  Eng.  (C,  S) ;   Swamp  White  Oak, 
Q.   platanoides   (Lam.)    Sudw.,  or  Q.   bicolor   Willd. 
(N,  C);  Cow  Oak,  Q.  michuaxii  Nutt.  (S,  C). 
b  Late  wood  without  distinct  radial  lines  or  patches,   but 
with  tangential  or  with  dotted  markings. 
ax  Pores  in  late  wood  numerous.     (For  bx,  see  p.  92.) 
a1  Pores  in  late  wood  very  small,   very  numerous  and 
arranged  in  conspicuous  tangential  or  concentric  bands 
or  festoons,  broken  near  early  wood;  usually  producing 
wavy  or  zig-zag  markings  on  tangential  surface.    Wood 
parenchyma  not  visible  with  lens. 

a2  Pores  in  early  wood  in  few  to  several  rows  except 
sometimes  in  narrow  growth  rings;  open. 

*  In  the  white  oaks  of  the  South  where  the  growth  is  rapid  the  transition 
from  large  to  small  pores  is  often  nearly  as  gradual  as  in  the  red  oaks.  The 
pores  in  the  summer  wood  are  also  larger  and  more  distinct,  but  the  fact  that 
they  are  too  numerous  to  count  readily  with  a  lens  and  have  thin  walls  and 
angular  outlines  permits  ready  separation  into  the  white  oak  olass.  A  some- 
what similar  structure  has  been  observed  in  Quercus  garryana. 

t  In  Q.  prinus  the  pores  are  often  open  as  in  the  black  oak  group. 

t  One  finds  occasional  exceptions  to  this  statement.  Certain  grades  of 
white  oak  are  locally  known  as  "pink  oak"  on  account  of  the  color. 

§  For  evergreen  and  live  oaks  which  are  diffuse-porous,  see  p.  98. 


ECONOMIC   WOODS   OF   THE    UNITED    STATES  89 

a3  Rays  very  distinct.  Color  yellowish  or  gray.  No 
odor.  Wood  very  coarse-textured;  hard  and 
heavy;  sp.  gr.  .65-80.  Rays  heterogeneous.  Vessels 
with  spirals;  perforations  simple;  pits  into  ray  cells  half- 
bordered.  Hackberry,  Celtis  occidentalis  L.  (C,  N,  S) ; 
Sugarberry,  C.  mississippiensis  Bosc.  (S). 

b3  Rays  often  obscure  without  lens.  Color  dark  or 
chocolate-brown.  Odor  suggesting  licorice  some- 
times noticed.  Wood  coarse-textured,  wooly; 
straight-grained;  hard  and  heavy;  sp.  gr.  65-80. 
Rays  homogeneous.  Otherwise  as  in  preceding.  Slippery 
or  Red  Elm,  Ulmus  pubescens  Walt.,  or  U.  fulva 
Michx.  (C,  N,  S). 

b2  Pores  in  early  wood  mostly  in  a  single  row;  occasion- 
ally more  m  wide  growth  rings.  Rays  not  always  dis- 
tinct without  lens.  Woods  without  odor.  (Microscopic 
features  as  in  preceding.)  Elm.33 

a3  Pores  in  early  wood  rather  large  and  distinct, 
mostly  open,  forming  a  continuous  row  (Plate  III, 
Fig.  2),  sometimes  more  than  one  row.  Growth 
rings  often  very  uneven  and  widely  variable  in 
thickness  in  different  portions.  Texture  coarse 
and  wooly.  Color  light  brown  to  gray  or  nearly 
white.  Wood  very  tough  and  difficult  to  split; 
moderately  hard  and  heavy;  sp.  gr.  .60-.75. 
White  Elm,   U.  americana  L.  (C,  N).34 

b3  Pores  in  early  wood  small  to  minute,  mostly  closed 
with  tyloses  in  heartwood;  larger  pores  few  and 
rather  widely  separated  in  a  band  of  small  ones. 
Growth  rings  fairly  even  and  uniform.  Texture 
medium,  not  very  wooly.  Color  light  brown  to 
pinkish.  Woods  hard  to  very  hard;  heavy  and 
tough;  sp   gr.  .70-.85. 

a4  Bands  of  small  pores  in  late  wood  rather  few, 
narrower  than  intervening  spaces.  Growth 
rings  distinct.  Wood  straight-grained,  fairly 
easy  to  split.  Rock  or  Hickory  Elm,  U. 
racemosa  Thom.,  or  U.  thomasi  Sarg.  (C,  N).35 


90  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

b4  Bands  of  small  pores  in  late  wood  numerous, 
wider  than  intervening  spaces,  often  very  wavy 
and  branched.  Growth  rings  not  always  dis- 
tinct. Wood  cross-grained,  difficult  to  split. 
Winged  Elm,  U.  alata  Michx.  (S,  C);  Cedar 
Elm,  U.  crassifolia  Nutt.  (S). 

b1  Pores  in  late  wood  variable  in  size  from  fairly  large  to 
minute,  clustered,  associated  with  parenchyma  which 
often  is  confluent  into  tangential  bands  irregular  and 
broken  or  more  or  less  continuous  in  outer  portion  of 
wide  rings. 

a2  Woods  hard  and  heavy.  Odorless.  Color  pro- 
nounced. Tyloses  present  or  absent.  Rays  fine 
but  distinct. 

a3  Tyloses  present,  light-colored ;  gum  deposits  absent 
or  only  occasional. 

a4  Wood  decidedly  variable  in  density  but  not 
horn-like;  sp.  gr.  .55-.65.  Color  orange-yellow 
to  yellowish-brown,  not  uniform;  becoming 
russet-brown  upon  exposure.  Pores  only  par- 
tially filled  with  tyloses.  Band  of  pores  in  early 
wood  varying  from  narrow  to  broad.  Rays 
very  conspicuous  on  radial  surface.  Small  ves- 
sels with  spirals;  perforations  simple;  pits  into  ray  cells 
simple  or  half-bordered.  Rays  heterogeneous.  Red 
Mulberry,  Morus  rubra  L,  (C,  S).  (Plate  V, 
Fig.  1);  White  Mulberry,  M.  alba  L.,  (Int.). 
b4  Woods  extremely  hard,  like  horn;  sp.  gr.  .77-.84. 
Color  of  freshly  exposed  wood  mostly  yellow 
(see  below).  All  pores  of  heartwood  completely 
filled  with  tyloses.  Band  of  pores  in  early 
wood  narrow.  Rays  not  conspicuous  on  radial 
surface.  Small  vessels  with  spirals;  perforations  simple; 
pits  into  ray  cells  simple  or  half-bordered.  Rays  more 
or  less  heterogeneous,  or  with  considerable  irregularity 
in  the  shape  of  the  cells. 

a5  Color  of  freshly  exposed  wood  golden  yellow, 
becoming  orange-brown  upon  exposure  to 
sunlight;  usually  with  rather  distinct  reddish 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  91 

streaks    showing    on    longitudinal    surface. 
Lustre  high.     Very  small  pin  knots  due  to 
thorns  common.     Wood  usually  knotty  and 
cross-grained,   without   worm   holes.     Osage 
Orange,  Toxylon  pomiferum  Raf.,  or  Madura 
aurantiaca  Nutt.,  (C,  S).    Plate  III  (Fig.  4).36 
b5  Color  varying  from  golden-yellow  to  brown, 
often  greenish  in  young  trees;  usually  uni- 
form in  same  specimen;  not  striped  with  red. 
Lustre  not   so   high   as  in   preceding;   wood 
mostly    straighter-grained    and    freer    from 
knots.     Large  worm  holes  common.     Black 
or    Yellow    Locust,    Robinia    pseudacacia    L. 
(C,  A).     Plate  III  (Fig.  3). 37 
b3  Tyloses  absent  or  rare,  not  light-colored;  dark- 
colored  gum  deposits  present. 
a4  Wood   parenchyma    conspicuous   in    numerous 
very  irregular  tangential  bands  which  include 
the  pores.     Pores  in  late  wood  varying  in  size 
from  minute  to  as  large  sometimes  as  in  early 
wood;  arrangement  very  irregular.     Dark  red 
gum  deposits  in  vessels  conspicuous,  showing  as 
dark  wavy  lines  on  tangential  surface.     Wood 
dull   mahogany   color;   thin   sapwood   greenish 
yellow.      Sp.  gr.   .77.      Vessels  without  spirals;    per- 
forations simple;  pits  into  ray  cells  half-bordered.     Rays 
homogeneous.      Mesquite   or  Algaroba,   Prosopis 
juli flora  (Schwartz)  de  C.  (Rs).38 

b4  Wood  parenchyma  mostly  in  patches  about  the 
pores  in  late  wood,  sometimes  confluent  in 
outer  portion.  Pores  in  outer  portion  of  growth 
ring  all  very  small;  distribution  fairly  regular. 
Gum  deposits  usually  inconspicuous.  Sp.  gr. 
.67-. 70.  Small  vessels  with  spirals;  perforations  simple; 
pits  into  ray  cells  half-bordered.  Rays  mostly  homoge- 
neous. 

a5  Pores  in  outer  portion  of  late  wood  usually 
in  groups  of  5-20;  individual  pores  visible 
under   lens.     Sapwood    thin.     Texture    very 


92  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

coarse.     Color   light   cherry-red   to   reddish- 
brown.     No  small  pin  knots  due  to  thorns. 
Kentucky  Coffee  Tree,*  Gymnocladus  dioicus 
Koch,  or  G.  canadensis  Lam.  (C).     (Plate  III, 
Fig.  5.) 
b5  Pores  in  outer  portion  of  late  wood  minute 
and  usually  in  groups  of   10-25;  individual 
pores  mostly  invisible  under  lens.     Sapwood 
thick.     Texture    moderately    coarse.     Color 
as   above.     Small   pin   knots   due   to   thorns 
common.     Honey   or    Sweet   Locust,   Thorn 
Tree,  Gleditsia  triacanthos  L.  (C,  S).     (Plate 
III,  Fig.  6.) 
b2  Woods  light  and  soft.     Odor  characteristic.     Color 
not     pronounced;     mostly     light     brown.     Tyloses 
present. 

a3  Rays  fine  but  very  distinct.  Odor  aromatic  or 
spicy,  usually  pronounced.  Color  light  orange- 
brown.  Texture  coarse.  Sp.  gr.  about  50.  Vessels 
without  spirals;  perforations  simple;  pits  into  ray  cells  half- 
bordered  or  simple.  Rays  heterogeneous  (Fig.  3,  A,  p. 
24).  Sassafras,  Sassafras  variifolium  (Salisb.) 
Ktze.,  or  S.  sassafras  Karst.  (S,  C).39 
b3  Rays  indistinct  without  lens.  Odor  mild,  some- 
what suggesting  kerosene.  Color  light  brown  to 
chestnut,  appearing  somewhat  bluish  on  ends  of 
specimen.  Texture  rather  fine.  Wood  lighter 
and  softer  than  preceding;  sp.  gr.  40-45.  Small 
vessels  with  spirals;  all  perforations  simple;  pits  into  ray 
cells  half-bordered  or  simple.  Rays  heterogeneous.  Com- 
mon Catalpa  or  Indian  Bean,  Catalpa  bignoniodes 
Walt.,  or  C.  catalpa  (L.)  Karst.  (C,  S);  Hardy 
Catalpa,  C.  speciosa  Ward.  (C).40 
bx  Pores  in  late  wood  few,  solitary,  or  sub-divided  radially 
into  2-4.     Woods  odorless  and  tasteless. f 

*  This  tree  is  sometimes  called  "mahogany"  in  eastern  U.  S. 

f  In  this  group  of  woods,  which  includes  ash,  persimmon  and  hickory,  the 
sapwood,  which  is  wide  and  white  is  more  commonly  employed  than  the  heart- 
wood  for  such  purposes  as  implement  stock  (ash),  tool  handles  and  wheel  stock 
(hickory),  and  shuttles  (persimmon). 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  93 

I1  Wood  parenchyma  about  pores  in  late  wood  and  often 
extending  wing-like  from  them;  may  become  confluent 
into  irregular  tangential  or  concentric  lines,  especially 
near  outer  margin  of  wide  growth  rings;  parenchyma 
also  terminal.  Pores  in  late  wood  all  much  smaller 
than  those  in  early  wood;  the  latter  usually  in  a  rather 
broad  zone,  3-10  pores  wide  (rarely  1-2).  Rays 
scarcely  distinct  without  lens.  Vessels  without  spirals; 
perforations  simple;  pits  into  ray  cells  half -bordered.  Rays  homo- 
geneous. Terminal  parenchyma  thick-walled,  abundantly  and 
irregularly  pitted.  Ash.*41 

a2  Pores  in  late  wood  rarely  joined  by  wood  paren- 
chyma.    Wood  of  medium  hardness  and  strength. 

a3  Pores  in  late  wood  isolated,  few,  large;  in  early 
wood  in  very  broad  zone,  often  over  one-half 
width  of  ring.  Wood  comparatively  light  and 
soft;  sp.  gr.  .47.  Color  decidedly  brown.  Ray 
cells  small.  Black  or  Brown  Ash.  F.  nigra  Marsh. 
(C,  N)  (Plate  V,  Fig.  2). 

b3  Pores  in  late  wood  in  radial  groups  of  2-5,  and  near 
outer  margin  of  growth  ring  somewhat  tangen- 
tially  grouped;  in  early  wood  in  zone  of  medium 
width,  usually  less  than  one-third  of  ring.  Color 
light  brown,  often  with  reddish  tinge.  Wood 
moderately  hard  and  strong.  Sp.  gr.  .57.  Ray 
cells  large.     Oregon  Ash,  F.  oregona  Nutt.  (P). 

b2  Pores  in  late  wood  usually  joined  tangentially  by 
wood  parenchyma.  Wood  mostly  very  hard  and 
strong,  sp.  gr.  .63-J2.  Color  gray-brown,  often 
with  reddish  tinge;  sapwood  white. 

a3  Pores  in  early  wood  in  rather  broad  zone;  nu- 
merous. 


*  The  specific  determination  of  the  ash  woods  is  often  difficult  or  impossible. 
Lumbermen  usually  recognize  two  kinds,  namely,  white  and  brown.  These 
two  unequal  groups  are  readily  distinguishable  by  their  gross  features.  Some 
of  the  wood  from  southern  swamp-grown  trees  has  the  structure  of  white  ash 
but  is  very  light,  soft  and  brash;  sp.  gr.  .38.  It  is  sometimes  called  "punk 
ash"  or  "  soft  ash." 


94  ECONOMIC   WOODS   OF  THE   UNITED   STATES 

a4  Lines  of  pores  in  late  wood  short,  narrow,  com- 
posed of  few  pores  and  considerable  wood  paren- 
chyma; mostly  near  outer  margin  of  growth 
ring;  occasionally  absent  or  very  indistinct  in 
narrow  rings.  White  Ash,  Fraxinus  americana 
L.  (C,  N).4i 

b4  Lines  of  pores  in  late  wood  long,  narrow,  promi- 
nent, composed  of  abundant  wood  parenchyma 
and  inconspicuous  pores;  usually  well  distrib- 
uted. Blue  Ash,  F.  quadrangulata  Michx.  (C); 
Red  Ash,  F.  pennsylvanica  Marsh.  (N). 

b3  Pores  in  early  wood  in  rather  narrow  zone;  fairly 
numerous.  Lines  of  pores  in  late  wood  quite 
long  and  conspicuous;  well  distributed.  Green 
Ash,  F.  lanceolata  Borh.  (C,  N,  S);  Pumpkin 
Ash,  F.  profunda  Bush.  (C). 

b1  Wood  parenchyma  in  numerous  fine  concentric  lines 
independent  of  pores.  Pores  in  late  wood  sometimes 
approaching  in  size  those  in  early  wood  which  are  not 
abundant  and  usually  arranged  in  a  very  irregular  zone. 

a2  "Ripple  marks"  (see  p.  39)  plainly  visible  on  tan- 
gential section;  wavy;  60  to  80  per  inch.  Lines  of 
wood  parenchyma  indistinct  without  lens;  finer 
than  the  rays.  Pores  open.  Color  of  heartwood 
of  old  trees  dark  brown  to  black,  often  streaked; 
sapwood  white  or  gray.  Wood  very  hard,  heavy 
and  strong;  sp.  gr.  .79.  Rays  in  horizontal  seriation; 
fairly  uniform  in  height;  1-2  (rarely  3)  cells  wide;  cells 
large;  heterogeneous.  (Plate  IV,  Figs.  4,  5.)  Vessels  without 
spirals;  perforations  simple;  pits  into  ray  cells  half -bordered. 
Persimmon,  Diospyros  virginiana  L.  (S,  C).43 

b2  "  Ripple  marks  "  absent.  Lines  of  wood  parenchyma 
distinct  as  the  rays;  visible  without  lens.  Pores 
partially  or  wholly  closed  with  tyloses.  Color  of  heart- 
wood  brown  to  reddish-brown ;  sapwood  white,  often 
with  pinkish  tinge  and  sometimes  with  dark  reddish 
or  rusty  streaks.  Rays  irregularly  disposed;  not 
uniform  in  height  or  shape;    1-5  cells  wide;  cells  small; 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  95 

somewhat  heterogeneous.  (Plate  IV,  Fig.  3.)  Vessels  without 
spirals;  perforations  simple;  pits  into  ray  cells  simple  or  half- 
bordered.  Hickory.*44 

a3  Wood  very  hard,  heavy  (sp.  gr.  .80-85),  tough, 
strong,  resilient.  Wood  fibres  normally  very  thick- 
walled,  t  Shagbark,  Hicoria  ovata  Brit.  (C,  N) 
(Plate  IV,  Fig.  3) ;  Big  Shellbark,  H.  laciniosa  Sarg. 
(C);  Mocker  Nut,  H.  alba  Brit.  (C,N,S);  Pignut, 
H.  glabra  Brit.  (C,  N,  S). 

b3  Wood  hard,  heavy  (sp.  gr.  .70-.75),  brittle,  fairly 
strong.  Wood  fibres  comparatively  thin-walled.  Pecan 
H.  -pecan  Brit.  (S,  C) ;  Nutmeg  Hickory,  H .  myris- 
ticceformis  Brit.  (S);  Bitternut,  H.  minima  Brit. 
(C,  N,  S);  Water  Hickory,  H.  aquatica  Brit.  (S).f 

B  Diffuse-porous  Woods.  Pores  fairly  uniform  in  size  and  dis- 
tribution throughout  growth  ring;  occasionally  more  numerous 
and  very  often  somewhat  larger  in  early  wood,  but  without 
forming  a  distinct  ring  or  band. 

a  Pores  variable  from  large  to  small,  all  or  at  least  a  portion 
of  them  readily  visible  to  the  unaided  eye;  comparatively 
few  to  numerous.  Large  vessels  very  distinct  on  longi- 
tudinal surface.  Woods  (except  Juglans  cinerea)  moder- 
ately to  extremely  dense.     (For  b,  see  p.  99.) 

a1  All  rays  fine.     Pores  not  in  continuous  radial  lines. 
(For  b1,  see  p.  98.) 

a2  Pores  comparatively  large  in  early  wood,  diminishing 
in  size  toward  outer  margin  of  growth  ring;  some- 
times approaching  ring-porous.  Growth  rings  dis- 
tinct.    Vessels  without  spirals;  perforations  simple. 

a3  Wood  parenchyma  in  numerous  very  fine  concen- 
tric lines,  independent  of  pores.  Pores  often  in 
echelon  arrangement;  solitary  or  in  radial  groups 

*  Specific  distinction  within  the  two  groups  of  hickory  woods  is  ordinarily 
not  possible.  The  commercial  names  "red  hickory"  and  "white  hickory" 
refer  to  heartwood  and  sapwood,  respectively.  By  "second-growth  hickory" 
is  meant  wide-ringed  wood  and  particularly  the  sapwood. 

t  Occasional  exceptions  to  this  general  rule  have  been  noted. 

%  Hicoria  aquatica  is  so  nearly  diffuse-porous  that  it  can  usually  be  dis- 
tinguished from  the  other  species. 


96  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

of  2-5;  tyloses  present.  Color  brown  or  purplish; 
never  yellow.  Rays  fine,  scarcely  visible  to  un- 
aided eye;  1-4  seriate,  few  to  30  cells  high;  mostly  homo- 
geneous. Pits  between  vessels  and  ray  cells  mostly  simple. 
Growth  rings  terminated  by  narrow  band  of  very  thick- 
walled,  flattened  wood  fibres.  Walnut.45 

a4  Wood  rather  dense;  sp.  gr.,  .60-.70.  Odor  mild 
but  characteristic.  Color  rich  dark  or  chocolate- 
brown  or  purplish;  sometimes  variegated.  Sap- 
wood  usually  rather  wide.  Wood  parenchyma  with 
abundant  crystals.  Ray  cells  circular  (tangential  section). 
Black  Walnut,  Juglans  nigra  L.  (C,  A)  (Plate 
IV,  Fig.  6);  California  Walnut,  J.  calif ornica 
Wats.  (Ps).* 

b4  Wood  light  and  soft;  sp.  gr.  .35-45.  Odorless. 
Color  light  chestnut  brown  with  darker  zones. 
Sapwood  very  thin.  Crystals  absent.  Ray  cells 
small  and  compressed  laterally.  Butternut,  White 
Walnut,  J.  cinerea  L.  (C,  N). 

b3  Wood  parenchyma  about  pores  and,  in  late  wood, 
joining  groups  of  pores  into  irregular  tangential 
lines.  Pores  irregularly  disposed;  solitary  or  in 
short  radial  groups.  Tyloses  absent.  Color  yel- 
low. Wood  dense;  sp.  gr.  .60-70.  Rays  fine,  1-6, 
mostly  3-4,  cells  wide  and  few  to  40  cells  high;  mostly 
heterogeneous.  Pits  between  vessels  and  ray  cells  half- 
bordered.  Terminal  fibres  flattened  but  not  thicker-walled 
than  others.  Yellow-wood,  Cladrastis  lutea  (Michx. 
f.)  Koch.  (Sc). 

b2  Pores  of  approximately  same  size  throughout  growth 
ring;  no  tendency  to  become  ring-porous.  Growth 
rings  not  always  distinct. 

a3  Wood  parenchyma  in  tangential  lines.  "Ripple 
marks"  present  or  absent.  Pores  resinous  or 
gummy. 

*  In  the  Yale  collection  is  a  board  of  Juglans  calif  ornica  in  which  the  late 
wood  is  much  lighter  in  color  and  the  fibres  much  thinner-walled  than  in  early 
wood. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  97 

a4  Wood  parenchyma  conspicuous  in  few  widely 
separated  lines,  apparently  terminating  growth 
rings;  also  about  pores.  " Ripple  marks,"  when 
present,  readily  visible  to  unaided  eye;  about 
50  per  inch.  Rays  fine  but  distinct.  Pores 
rather  large,  uniform  in  size  and  distribution, 
solitary  or  in  radial  groups  of  2-3;  often  filled 
with  dark  red  gum  or  with  white  deposits. 
Gum  ducts  occasionally  present  in  peripheral 
row.  Native  wood  hard  and  heavy;  sp.  gr.  .73; 
color  rich  reddish  brown;  often  highly  figured.* 
Vessels  without  spirals;  perforations  simple;  pits  into 
ray  cells  half-bordered.  Rays  1-4  cells  wide,  few  to  20 
or  more  cells  high;  heterogeneous.  Wood  fibres  often 
finely  septate;  pits  simple.  Mahogany,  Swietenia 
mahagoni  Jacq.  (T).46 

b4  Wood  parenchyma  in  numerous  fine,  wavy 
lines.  "Ripple  marks"  always  present,  uni- 
form, invisible  to  unaided  eye  but  distinct  with 
lens;  about  250  per  inch.  Rays  very  fine,  in- 
distinct. Pores  not  large  but  distinct,  variable 
in  size  and  distribution;  solitary  or  in  radial 
groups  of  2-3.  Color  dark  yellowish  brown 
with  greenish  tinge,  not  uniform;  becomes  very 
dark  and  oily  in  old  trees.  Wood  with  inter- 
locked or  criss-cross  grain;  extremely  dense;  sp. 
gr.  1.14.  Vessels  without  spirals;  perforations  simple; 
pits  into  ray  cells  small,  half -bordered.  Rays  uniseriate; 
homogeneous;  arranged  in  horizontal  seriation.  Wood 
fibres  not  septate;  pits  bordered.  Lignum-vitae,  Guai- 
acum  sanctum  L.  (T). 


*  The  true  mahogany  is  native  to  a  region  extending  from  the  extreme 
.southern  part  of  Florida  to  the  West  Indies,  and  along  the  Gulf  Coast  in  Mexico 
from  Tampico  through  Central  America  into  the  northern  part  of  South 
America.  There  is  a  wide  variation  in  the  properties  of  the  wood  from  differ- 
ent localities.  That  from  Florida  is  like  the  hardest  and  heaviest  of  the  West 
Indian  grades.  Mexican  mahogany  is  the  most  variable  in  quality,  some  of 
it  being  light,  soft  and  porous  like  Spanish  cedar.  There  are  many  other 
woods  which  appear  on  the  market  as  mahogany.  See  Mell's  "True  Mahog- 
any," Bui.  No.  474,  U.  S.  Dept.  Agr.,  1917. 


98  ECONOMIC   WOODS    OF   THE   UNITED   STATES 

b3  Wood  parenchyma  about  pores;  not  in  tangential 

lines.     No  "ripple  marks."     Pores  not  resinous 

or  gummy. 

a4  Wood  extremely  dense;  sp.  gr.  .83;  fibres  much 
interlaced.  Alternate  bands  of  wood  varying 
in  density  and  direction  of  fibre  common,  but 
growth  rings  not  sharply  defined.  Pores  con- 
spicuous, irregularly  distributed,  often  in  diag- 
onal chains  which  may  be  zig-zag;  tyloses 
present.  Rays  very  fine,  indistinct.  Vessels 
without  spirals;  perforations  simple;  pits  into  ray  cells 
half-bordered  or  simple.  Rays  1-2,  occasionally  more, 
cells  wide  and  1-25  cells  high;  somewhat  heteroge- 
neous. Blue  Gum,  Eucalyptus  globulus  Lab.  (Int., 
Ps,  T).47 

b4  Wood  moderately  dense,  sp.  gr.  .65;  grain  vari- 
able from  straight  to  wavy.  Growth  rings  dis- 
tinct, due  to  denser  band  of  late  wood.  Pores 
rather  small,  mostly  in  radial  groups  of  2-6, 
fairly  uniformly  distributed;  tyloses  absent. 
Rays  fine.  Odor  spicy.  Vessels  without  spirals; 
perforations  simple;  pits  into  ray  cells  half -bordered  or 
simple.      Rays  2-3  seriate,  few  to  25  cells  high;   mostly 

homogeneous.  California  Laurel,  Pepperwood, 
Umbellularia  calif ornica  (H.  &  A.)  Nutt.  (P). 
b1  Some  of  the  rays  usually  very  broad.*  Pores  some- 
what variable  in  size  but  distinct;  arranged  in  radial 
lines  or  bands  between  broad  rays,  extending  across 
the  growth  ring  and  often  continuous  from  one  ring  to 
another.  Wood  parenchyma  commonly  in  concentric 
lines  as  well  as  about  pores,  frequently  conspicuous. 
Wood  very  dense;  sp.  gr.  .85-95.  Color  light  to  dark 
brown,  sometimes  tinged  with  red.  Evergreen  and 
Live  Oak  Group.48  Quercus  virginiana  Mill.  (8);  Q. 
agrifolia  Nee.  (Ps);  Q.  chrysolepis  Liebm.  (Ps.);  Q. 
wislizeni  A.  de  C.  (Ps);  Tanbark  Oak,  Q.  densifiora 
H.  &  A.,  or  Pasania  densifiora  Oerst.  (P).49 

*  It  is  not  uncommon  to  find  specimens  of  the  woods  of  this  group  without 
broad  rays,  though  in  such  cases  there  is  a  tendency  to  aggregation  of  the  uni- 
seriate  rays. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  99 

b  Pores  small  to  minute,*  often  indistinct  without  lens 
(especially  in  dense  woods),  mostly  very  numerous  and 
well  distributed  throughout  growth  ring.  Vessels  not 
conspicuous. 

a1  Woods  dense  to  moderately  so.f     Rays  variable  from 
fine  to  broad.     (For  b1,  see  p.  105.) 

a2  Pores  in  radial  lines,  not  crowded  laterally.     Wood 
parenchyma  in  tangential  lines. 

a3  Lines  of  wood  parenchyma  visible  with  lens  on 
moist  cross  section.  Pores  in  early  wood  visible 
to  unaided  eye.  Wood  dense,  difficult  to  split. 
Vessels  with  spirals;  perforations  simple;  pits  into  ray  cells 
simple  or  nearly  so.  Wood  fibres  without  spirals;  pits 
bordered. 

a4  Rays  all  very  fine,  indistinct.  Pores  near  pe- 
riphery of  growth  ring  minute  and  in  groups 
which  appear  to  the  unaided  eye  as  white  dots. 
Growth  rings  sometimes  sinuous;  distinct. 
Color  light  brown  or  roseate.  Sp.  gr.  .83.  Rays 
heterogeneous  in  part.  Hop  Hornbeam,  Ironwood, 
Ostrya  virginiana  Koch.  (N,  C)  (Plate  V,  Fig.  6). 

b4  Some  of  the  rays  broad,  aggregated.  Pores  in 
late  wood  sometimes  as  in  preceding.  Growth 
rings  always  sinuous;  distinct  or  fairly  so. 
Color  yellowish  white.  Sp.  gr.  .73.  Rays  homo- 
geneous. Blue  Beech,  Water  Beech,  or  Horn- 
beam, Carpinus  caroliniana  Walt.  (N,  C).50 

b3  Lines  of  wood  parenchyma  not  visible  with  lens. 
Pores  not  visible  without  hand  lens;  arranged  in 
regular  radial  lines;  no  white  dots.  Rays  distinct. 
Growth  rings  regular;  rather  indistinct.  Wood 
moderately  dense;  sp.  gr.  .51-.66,  average  .58; 
fairly  easy  to  split.     Color  chalky  white,   often 

*  In  a  few  woods  of  this  group,  particularly  Cottonwood  and  black  willow, 
the  pores,  at  least  in  early  wood,  are  readily  visible,  but  their  abundance  and 
the  softness  of  the  wood  permit  no  confusion  with  the  preceding  group. 

t  A  partial  exception  occurs  in  the  case  of  Nyssa,  some  of  the  species  of 
which  produce  light  and  soft  woods. 


100  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

bluish.  Vessels  with  spirals;  perforations  scalariform  with 
many  bars;  pits  into  ray  cells  half-bordered.  Wood  fibres 
with  spirals;  pits  bordered.  Rays  heterogeneous;  of  two 
kinds:  (1)  Large  (3-6  cells  wide  and  up  to  80  cells  high) 
with  all  except  marginal  cells  uniformly  low ;  (2)  fine  (mostly 
uniseriate  and  few  to  many  cells  high)  with  all  cells  large. 
Holly,  Ilex  opaca  Ait.  (S,  C). 

b2  Pores  not  in  radial  lines  although  often  in  short 
radial  groups;  frequently  crowded.  Wood  paren- 
chyma sometimes  in  tangential  lines  but  not  visible 
with  lens,  except  indistinctly  in  Cornus  and  occasion- 
ally in  Fagus. 

a3  Rays  quite  distinct  to  unaided  eye.     (For  b3,  see 
p.  103.) 

a4  Conspicuously  broad  rays  present;  not  aggre- 
gated. 

a5  Rays  nearly  all  broad,  numerous;  fairly  regu- 
larly disposed  and  conspicuous  on  tangential 
surface;  of  deeper  color  than  surrounding 
tissue,  producing  very  distinct  "silver  grain  " 
on  radial  or  "quarter-sawed"  surface.  Wood 
parenchyma  in  irregular  tangential  rows 
but  not  visible  with  lens.  Pores  crowded. 
Woods  fairly  dense,  usually  cross-grained, 
splitting  irregularly;  sp.  gr.  .47-57.  Color 
light  brown,  often  striped.  Late  wood  thin, 
of  lighter  color  than  the  early  wood.  Vessels 
without  spirals;  perforations  mostly  simple  but  often 
scalariform  with  few  bars;  bordered  pits  sometimes 
scalariform;  pits  into  ray  cells  half -bordered.  Rays 
homogeneous.  Wood  fibres  with  bordered  pits. 
Sycamore  or  Buttonball,  Platanus  occidentolis 
L.  (C,  N,  S);  P.  racemosa  Nutt.  (Ps);  P. 
wrightii  Wats.  (Rs).51 
b5  Only  a  portion  of  rays  broad ;  variable,  irregu- 
larly distributed;  readily  visible  on  tan- 
gential surface;  intermediate  rays  very  fine. 
Color  of  rays  not  pronounced,  hence  "silver 
grain  "  less  conspicuous  than  in  preceding 


ECONOMIC   WOODS   OF    THE   UNITED   STATES  101 

Wood  parenchyma  in  tangential  rows,  occa- 
sionally visible  with  lens.  Pores  crowded. 
Wood  dense;  usually  straight-grained;  sp.  gr. 
.63-.80,  average  .69.  Color  reddish  brown  to 
nearly  white;  uniform.  Late  wood  rather 
thick,  of  darker  color  than  the  spring  wood. 
Vessels  without  spirals;  large  perforations  simple,  small 
ones  often  scalariform;  pits  into  ray  cells  half-bordered 
or  simple.  Rays  heterogeneous.  Wood  fibres  with 
bordered  pits.  Beech,  Fagus  americana  Sw.,  or 
F.  grandifolia  Ehr.  (C,  N,  S).52 

b4  No  conspicuously  broad  rays  present. 

a5  Wood  parenchyma  in  somewhat  broken  tan- 
gential lines,  faintly  visible  in  part  with  lens 
on  moist  cross  section.  Rays  light  red  or 
pink  in  color,  very  distinct.  Color  roseate 
to  reddish-brown,  sometimes  with  greenish 
hue.  Wood  very  heavy,  hard  and  tough. 
Vessels  without  spirals;  perforations  scalariform  with 
many  bars;  bordered  pits  often  scalariform;  pits  into 
ray  cells  half-bordered.  Rays  heterogeneous.  Wood 
fibres  with  slit-like  pits  with  distinct  borders. 

a6  Wood  very  dense,  sp.  gr.  .76-.89,  average 
.82.  Rays  1-7  cells  wide,  few  to  80  cells  high. 
Flowering    Dogwood,    Cornus    florida    L. 

(N,  C,  S). 

b6  Wood  dense;  sp.  gr.  .75.  Rays  1-4  cells  wide, 
few  to  40  cells  high.  (Western)  Dogwood. 
Cornus  nuttallii  Aud.  (P.) 

b5  Wood  parenchyma  not  in  tangential  lines. 
Vessels  with  spirals;  perforations  simple;  pits  not 
scalariform;  pits  into  ray  cells  half-bordered. 

a6  Color  rich  reddish-brown  or  vinous.  Rays 
on  radial  surface  appear  considerably 
lighter  than  background.  Pores  numerous, 
solitary  or  in  groups,  often  radial,  of  2-6; 
usually  more  abundant  and  larger  in  early 
wood  but  with  gradual  transition.     Vessels 


102  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

plugged  at  intervals  with  dark  red  gum. 
Gum  ducts  common.  Wood  variable  in 
density;  sp.  gr.  .48-71,  average  .58.  Rays 
mostly  3-5  cells  wide,  occasionally  uniseriate,  and 
few  to  100  cells  high;  somewhat  heterogeneous. 
Wood  fibres  with  bordered  pits.  Black  Cherry, 
Primus  serotina  Ehrh.  (C,  N,  S). 

b6  Color  variable  from  very  light  to  decidedly 
reddish.  Rays  on  radial  surface  appear 
considerably  darker  than  background; 
variable  in  size.  Pores  not  crowded,  fairly 
evenly  distributed;  solitary  or  in  radial 
groups  of  2-3;  fairly  uniform  in  size 
throughout  growth  ring.  Grain  often 
curly,  " landscape,"  or  "birds-eye."  Rays 
homogeneous.  Wood  fibres  with  bordered  to  simple 
pits.    Maple.*53 

a7  Part  of  the  rays  comparatively  large, 
broader  than  the  pores,  conspicuous. 
Pith  flecks  rare.  Growth  rings  very  dis- 
tinct on  account  of  deeper-colored  late 
wood.  Wood  dense ;  ave.  sp.  gr.  .69.  Rays 
5-7  cells  wide  with  intermediate  rays  uniseriate. 
Hard,  Sugar,  or  Rock  Maple,  Acer  sac- 
charum  Marsh.  (N,  C.)54;  Black  Maple, 
A.  nigrum  Michx.  (N,  C). 

b7  With  less  variation  in  the  size  of  the  rays, 
the  large  ones  not  so  broad  as  the  pores; 
low,  inconspicuous.  Growth  rings  often 
indistinct.  Woods  variable  from  soft  to 
moderately  hard.     Uniseriate  rays  few. 

a8  Color  deep  and  rich.  Pith  flecks  un- 
common. Sp.  gr.  .49.  Oregon  Maple, 
A,  macrophyllum.  (P). 

*  Boxelder  or  ash-leaved  maple,  Acer  negundo  L.,  or  Negundo  aceroides 
Moench.  (N,  C,  S,  R),  and  its  varietal  form,  californicum  (T.  &  G.)  Sarg.  (Ps), 
produce  rather  light  (sp.  gr.  .43),  soft  woods,  cream-colored  or  yellowish  white. 
The  pores  are  small  and  numerous;  often  in  radial  groups  of  2-6.  Rays  are 
without  color. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  103 

b8  Color  pale,  often  with  greenish  tinge. 
Pith  flecks  very  common,  often  abund- 
ant. Sp.  gr.  .62.  Soft  or  Red  Maple, 
A.  rubrum  L.  (N,  C,  S);  Silver  Maple, 
A.  saccharinum  L.  (N,  C,  S). 
b3  Rays  indistinct  without  lens. 

a4  Wood  mostly  straight-grained,  easy  to  split. 
Growth  rings  usually  distinct.  Wood  paren- 
chyma scattered,  sometimes  in  broken  tangen- 
tial lines  in  outer  late  wood  and  in  a  single 
terminal  layer  usually  visible  as  a  faint  white 
line.  Vessels  without  spirals;  densely  pitted  with  ex- 
tremely small  bordered  pits  with  slit-like  openings ;  perfora- 
tions scalariform;  pits  into  ray  cells  half-bordered.  Rays 
1-5  cells  wide;  homogeneous.  Wood  fibres  with  bordered 
pits.  Birch.55 

a5  Wood  mostly  heavy,  hard  and  strong.     Color 
brown    tinged    with    red,    sometimes    deeply 
reddish;  often  figured.     Pith  flecks  rare. 
a6  Specific  gravity  .G9-.82,  average  .76.     Rays 
widest   of   genus,  bluntly  tapering;    cells  round 
(tangential  section).     Sweet,  Black  or  Cherry 
Birch,  Betula  lenta  L.  (S,  C,  N).* 
b6  Specific  gravity  .58-.72,  average  .66.     Rays 
narrower,  cells  flattened  laterally  (tangential  sec- 
tion).    Yellow    Birch,    B.    lutea    Michx.    f. 
(N,  C). 
b5  Wood  considerably  less  dense  than  in  pre- 
ceding group;  sp.  gr.  average  .58-.60.     Color- 
less or  light  brown.     Pith  flecks  common. 
a6  Pores  rather  large,  readily  visible  to  unaided 
eye.     Wood  rather  coarse-textured;  some- 
times cross-grained.     Sp.  gr.  .55-.60.    River 
or  Redf  Birch,  B.  nigra  L.  (S,  C,  N). 


*  The  woods  of  Betula  lenta  and  B.  lutea  appear  on  the  market  together 
without  distinction  as  to  species,  and  have  identical  uses.  The  former  is  some- 
what harder  and  stronger  as  a  rule. 

f  The  names  "red  birch"  and  "white  birch"  are  often  used  commercially 
to  designate  the  heartwood  and  sapwood,  respectively,  of  Betula  lenta  and  B. 
lutea. 


104  ECONOMIC   WOODS   OF   THE    UNITED    STATES 

b6  Pores  very  small,  indistinct  to  unaided  eye. 
Woods  fine-textured  and  straight-grained; 
lighter-colored  than  preceding.  Sp.  gr.  .46- 
.64.  Paper,  White*  or  Canoe  Birch,  B. 
papyrifera.  Marsh.  (N,  Rn,  Pn)56;  Gray 
Birch,  B.  populifolia  Marsh.  (N). 

b4  Woods  mostly  cross-grained,  tough  to  split. 
Growth  rings  usually  indistinct.  Wood  paren- 
chyma scattered,  not  in  tangential  lines  or  terminal. 

a5  Wood  very  dense;  sp.  gr.  about  .75.  Color 
reddish-brown  or  roseate;  sapwood  yellowish. f 
Pores  minute,  well  distributed,  very  numer- 
ous. Vessels  without  spirals;  bordered  pits  round; 
perforations  simple;  pits  into  ray  cells  half-bordered. 
Rays  3-4  cells  wide;  homogeneous.  Wood  fibres  with 
numerous  large  bordered  pits.  Apple,  Pyrus  mains 
L.  (Int.)57 

b5  Woods  variable  in  density.  The  denser  ones 
colorless  or  light  brown.  Grain  more  inter- 
locked than  preceding.  Rays  1-5  cells  wide; 
heterogeneous.  Vessels  mostly  without  spirals;  sca- 
lariform  bordered  pits  common;  perforations  sea- 
lariform  with  many  bars.  Pits  in  wood  fibres  not 
conspicuous. 

a6  Color  reddish-brown,  often  with  irregular 
dark  streaks  producing  "watered  "  effect  on 
smooth  longitudinal  surface;  sapwood  often 
variegated.  Lustre  rather  dull.  Pores 
minute,  abundant,  uniformly  distributed; 
tyloses  present.  Gum  ducts  occasionally 
present  in  peripheral  row.  Wood  mod- 
erately hard  to  rather  soft;  inclined  to 
warp;  sp.  gr.  .50-.60.  Vessels  without  spirals 
except    indistinctly    on    overlapping    ends   of   seg- 

*  The  names  "red  birch"  and  "white  birch"  are  often  used  commercially 
to  designate  the  heartwood  and  sapwood,  respectively,  of  Betula  lenta  or  B. 
lutea. 

f  In  the  use  of  applewood  for  handles  it  is  customary  to  steam  the  sapwood. 
This  treatment  produces  a  rich  uniform  color  resembling  that  of  black  cherry. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  105 

ments;  pits  into  ray  cells  simple  or  half-bordered; 
no  "resin  plates."  Rays  1-2  cells  wide,  few  to 
30  cells    high;     containing    dark    gum.     Red    or 

Sweet    Gum,    Gumwood,    "  Hazel,"    Li- 

quidambar  styraciflua  L.  (S,  C).  (Plate  VI, 
Fig.  I.)58 

b6  Color  brown  to  nearly  white,  fairly  uniform. 
Lustre   high.     Pores  variable  in   size  and 
abundance  in  different  species;  tyloses  ab- 
sent.   Gum  ducts  absent.    Light-colored  trans- 
verse "resin  plates"  may  be  present  in  vessels  and 
fibres  of  heartwood.*    Vessels  wholly  without  spirals. 
a7  Wood  usually  rather  dense,  tough  and 
strong;    sp.    gr.    .56-.75,    average    .64. 
Pores  minute,   not   crowded.     Black   or 
Sour  Gum,  Pepperidge,  Nyssa  sylvatica 
Marsh.  (C,  N,  S). 
b7  Wood  rather  light  and  soft;  tough  but 
not  strong;  sp.  gr.  .40-.56,  average  about 
.50.     Pores  small,  crowded.     Tupelo,  Bay 
Poplar,  N.  aquatica  L.  (S,  C);  N.  biflora 
Walt.  (S).59 

b1  Woods  mostly  light  and  soft.     Rays  fine.t 
a2  Rays  distinct  to  unaided  eye. 

a3  Growth  rings  terminated  by  distinct  light-colored 
line  of  parenchyma;  no  parenchyma  lines  within 
growth  ring.  No  "ripple  marks"  on  wood. 
Vessels  as  below;  tyloses  few,  thin-walled,  incon- 
spicuous. Woods  soft  but  firm,  occasional  speci- 
mens rather  hard;  straight-grained,  as  a  rule. 
Rays  fairly  uniform  for  each  species;  heterogeneous 
(marginal  cells  square  or  upright);  cell  walls  very  thick, 
abundantly  and  irregularly  pitted;  pits  into  vessels  often  in 
groups  with  common  border.  Terminal  parenchyma  in  2-3 
rows;  cells  thick-walled  and  very  irregularly  pitted  (tangen- 
tial section). 

*  See  author's  "Significance  of  Resinous  Tracheids,"  Botanical  Gazette, 

:  1  :  61-67,  (July  1918). 

t  A  partial  exception  occurs  in  Alnus  where  aggregate  rays  are  often  found. 


106  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

a4  Pores  rarely  in  radial  groups.  Color  widely- 
variable,  depending  upon  age  of  tree  and  locality 
of  growth,  from  clear  yellow  to  green,  brown  or 
purplish;  sapwood  often  variegated  or  striped, 
light  gray  or  nearly  white.  Curly  and  mottled 
grain  not  uncommon.  Sp.  gr.  .38-48,  average 
.42.  Vessels  with  round  or  elliptical  bordered  pits  in 
rows,  sometimes  scalariform  in  part;  without  spirals; 
perforations  scalariform  with  few  bars.  Rays  mostly 
3-seriate,  few  to  60,  mostly  20-40,  cells  high.  Poplar, 
Yellow  Poplar,  Tulip-tree,  White  wood,  Lirio- 
dendron  tulipifera  L.  (C,  N).  (Plate  VI,  Figs. 
2,  4).60 
b4  Pores  often  in  radial  groups  of  3-8.  Vessels  with 
scalariform  bordered  pits  (Plate  VI,  Fig.  3);  spirals  in- 
distinct. 

a5  Color  mostly  yellow  or  greenish;  often  closely 
resembling     Liriodendron.     Sp.    gr.    .42-54, 
average    .47.      Vessel    perforations    usually    simple. 
Rays  mostly  homogeneous,  2-seriate  and  10-15  cells 
high.     Cucumber  Tree,   Magnolia   acuminata 
L.  (C,  A). 
b5  Color  light  brown.     Sp.  gr.  about  .50.     Vessel 
perforations  scalariform   with  few  bars.     Rays   hete- 
rogeneous;   2-4  cells  wide,  mostly  50-100  cells  high. 
White  or  Sweet  Bay,  M.  glauca  L.  (S). 
b3  Wood  parenchyma  not  visible  with  lens.     Wood 
elements,    except    rays,    in    storied    arrangement, 
producing  somewhat  indistinct  "ripple  marks  "  on 
tangential  surface;  55-60  per  inch.     Wood  light, 
soft,  compact,  moderately  strong;  sp.  gr.  .38-.52, 
mostly  between  .40-45.       Color  light  brown  to 
creamy  white.     Rays  of  two  general  sizes:  (1)  uniseriate 
and  10-15  cells  high;    (2)  3-5  cells  wide  and  50-100  cells 
high;    mostly  homogeneous.     Vessels  with  spirals;  tyloses 
absent;  perforations  simple;  bordered  pits  not  scalariform; 
pits  into  ray  cells  small,  half-bordered.      Wood  parenchyma 
in  numerous  fine  tangential  lines.     Basswood,  Lin,  Tilia 
americana  L.   (N,  C);   T.  pubescens  Ait.   (S,  C); 
T.  heterophylla  Vent.  (A,  C,  S).61 


ECONOMIC   WOODS   OF   THE   UNITED    STATES  107 

b2  Rays  indistinct  to  unaided  eye  and  often  with  lens, 
except  for  occasional  aggregate  rays  in  Alnus  oregona* 
a3  Rays  fairly  distinct  with  lens. 

a4  Wood  of  very  fine  texture.  Pores  minute,  in- 
visible without  lens,  very  uniformly  distributed. 
Color  pale  yellow  to  nearly  white.  Lustrous. 
Growth  rings  terminated  by  fine  line  of  wood 
parenchyma.  Pith  flecks  absent.  Wood  light, 
soft,  compact,  tough,  often  with  curly  or  inter- 
locked grain;  sp.  gr.  .42-50.  Vessels  with  spirals; 
perforations  simple;  pits  into  ray  cells  half -bordered; 
often  grouped.  (Fig.  3,  C,  p.  24).  Rays  all  uniseriate; 
heterogeneous. 

a5  "Ripple  marks"  distinct  on  tangential  sur- 
face; fairly  regular;  65-70  per  inch;  all  ele- 
ments storied.  Yellow  Buckeye,  JZsculus 
octandra  Marsh.  (C).62 
b5  "Ripple  marks"  absent  or  local;  very  irreg- 
ular. Ohio  Buckeye,  A.  glabra  Willd.  (C). 
(Plate  VI,  Figs.  5,  6);  California  Buckeye,  A. 
calif ornica  Nutt,  (Ps). 

b4  Wood  of  only  moderately  fine  texture.  Pores 
barely  visible  to  unaided  eye;  somewhat  larger 
and  more  numerous  in  early  wood;  often  in 
short  radial  groups.  Color  light  brown  tinged 
with  red;  surface  of  freshly  cut  sapwood  soon 
stained  greenish-brown  upon  exposure.  Lustre 
dull.  Pith  flecks  common.  "Ripple  marks" 
absent  except  possibly  over  small  areas.  Wood 
light,  firm,  moderately  strong;  sp.  gr.  about  .48. 
Growth  rings  not  terminated  by  parenchyma. 
Broad  rays  occasionally  present,  being  aggre- 
gates of  small  rays.  (Plate  V,  Figs.  3,  4). 
Ordinary  rays  1-2  cells  wide;  homogeneous.  Vessels 
without  spirals;  perforations  scalariform,  few  to  many 
bars;  pits  into  ray  cells  half -bordered.  Wood  paren- 
chyma scanty,  diffuse.  Red  Alder,  Alnus  oregona 
Nutt.,  or  A.  rubra  Bong.  (P).63 

bs  Rays  indistinct  even  under  lens. 


108  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

a4  Color  of  wood  reddish-brown,  usually  variable. 
Lustre  dull.  Texture  coarse.  Pores  very 
abundant,  readily  visible  to  unaided  eye;  smaller 
in  late  wood  and  sometimes  in  irregular  tan- 
gential arrangement  in  wide  growth  rings. 
Wood  light  and  soft  but  fairly  tough;  sp.  gr.  .41- 
.47.  Wood  parenchyma  terminal  in  1-2  rows,  usually 
invisible  with  lens.  Vessels  without  spirals;  perforations 
simple;  pits  into  ray  cells  simple.  Rays  uniseriate;  het- 
erogeneous. Black  Willow,  "  Brown  Cotton- 
wood," Salix  nigra  Marsh.     (C,  N,  S,  Rs,  Ps).64 

b4  Color  pale  brown,  grayish  or  white.  Woods 
very  light  and  soft.  Growth  ring  terminated  by 
fine  light-colored  line  of  parenchyma,  more  or 
less  distinct.  Vessels  without  spirals;  perforations 
simple;  pits  into  ray  cells  simple.  Rays  uniseriate; 
homogeneous. 

a5  Texture  rather  coarse  and  wool}'.  Lustre 
dull.  Pores  abundant,  visible  without  lens, 
smaller  in  late  wood  and  sometimes  in  irregu- 
lar tangential  arrangement  in  wide  growth 
rings.  Sp.  gr.  .32-.48,  average  about  .40. 
Poplar,  Cottonwood,  Populus  deltoides  Marsh. 
(N,  C,  S,  R)65;  P.  heterophylla  L.  (S,  C);  P. 
trichocarpa  T.  J.  G.  (P). 

b5  Texture  very  fine  and  silky.  Lustre  high. 
Pores  abundant,  usually  invisible  without 
lens;  fairly  uniform  in  size  and  arrangement. 
Sp.  gr.  .36-51,  mostly  .40-45.  Aspen,  Pop- 
lar, Popple,  P.  tremuloides  Michx.  (N,  C,  R, 
P);  P.  grandidentata  Michx.  (N,  C).66 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  109 

REFERENCES 
Wine: 

Bailey,  Irving  W.:  The  Structure  of  the  Wood  in  the  Pinese.  Bot.  Gaz., 
48:1:47-5,%  July  1909. 

Bailey,  Irving  W.:  Anatomical  Characters  in  the  Evolution  of  Pinus. 
Am.  Nat.,  44:  284-293,  May  1910. 

Hall,  William  L.,  and  Maxwell,  Hu:  Uses  of  the  Commercial  Woods 
of  the  United  States,  II.  Pines.     Bui.  99,  U.  S.  Forest  Service,  1911. 

Burgerstein,  Alfred:  Vergleichende  anatomische  Untersuchungen  des 
Fichten-  und  Larchenholzes.  Denkschrift  f.  kaiserl.  Akad.  Wissensch.  Math.- 
Natur.  Classe,  59:  6:  214-215,  1894. 

*White  Pine  Group: 

Rockwell,  F.  I.:  The  White  Pines  of  Montana  and  Idaho:  Their  Distri- 
bution, Quality  and  Uses.     For.  Quarterly,  9:  2:  219-231,  June  1911. 

z Pinus  strobus: 

Spalding,  V.  M.:  The  White  Pine.     Bui.  22,  U.  S.  Div.  Forestry,  1899. 

Detwiler,  Samuel  B.:  The  White  Pine.  Amer.  For.,  22:  271:  387-394, 
July  1916. 

4Pinus  lambertiana: 

Larsen,  Louis  T.,  and  Woodbury,  T.  D.:  Sugar  Pine.  Bui.  426,  U.  S. 
Forest  Service,  1916. 

Cooper,  Albert  W. :  Sugar  Pine  and  Western  Yellow  Pine  in  California. 
Bui.  69,  U.  S.  Forest  Service,  1906. 

5Pinus  edulis: 

Phillips,  F.  J.:  A  Study  of  Pifion  Pine.  Bot.  Gaz.,  48:  3:  216-223,  Sept. 
1909. 

Heller,  A.  A.:  The  Nut  Pine.     Muhlenbergia,  5:  31-35,  1909. 

6Pinus  resinosa: 

Woolsey,  Theodore  S.,  Jr.,  and  Chapman,  Herman  H.:  Norway  Pine 
in  the  Lake  States.     Bui.  139,  U.  S.  Forest  Service,  1914. 

7Pinus  contorta: 

Mason,  D.  T. :  The  Life  History  of  Lodgepole  Pine  in  the  Rocky  Moun- 
tains.    Bui.  154,  U.  S.  Forest  Service,  1915. 

Mason,  D.  T.:  Utilization  and  Management  of  Lodgepole  Pine  in  the 
Rocky  Mountains.     Bui.  234,  U.  S.  Forest  Service,  1915. 

BPinus  ponderosa: 

Munger,  Thornton  T.:  Western  Yellow  Pine  in  Oregon.  Bui.  418,  U.  S. 
Forest  Service,  1917. 

Cooper,  Albert  W.:  Sugar  Pine  and  Western  Yellow  Pine  in  California. 
Bui.  69,  U.  S.  Forest  Service,  1906. 

Woolsey,  Theodore  S.,  Jr.:  Western  Yellow  Pine  in  Arizona  and  New 
Mexico.     Bui.  101,  U.  S.  Forest  Service,  1911. 

Zimmermann,  C.  W.  :  Tests  of  Western  Yellow  Pine  Car  Sills,  Joists,  and 
'Small  Clear  Pieces.     Bui.  497,  U.  S.  Forest  Service,  1917. 


110  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

^Southern  Pines: 

Fernow,  B.  E.:  Southern  Pine:  Mechanical  and  Physical  Properties.  Cir. 
12,  U.  S.  Div.  Forestry,  1896. 

Mohr,  Charles,  and  Roth,  Filibert:  The  Timber  Pines  of  the  Southern 
United  States,  together  with  a  Discussion  of  the  Structure  of  their  Wood. 
Bui.  13  (rev.  ed.),  U.  S.  Div.  Forestry,  1897. 

Betts,  H.  S.:  Properties  and  Uses  of  the  Southern  Pines.  Cir.  164,  U.  S. 
Forest  Service,  1909. 

Record,  Samuel  J.:  Southern  Yellow  Pine  for  Structural  Purposes. 
American  Architect,  Apr.  11,  1917,  pp.  223-228. 

10Pinus  caribcea: 

Mattoon,  Wilbur  R.:  Some  Characteristics  of  Slash  Pine.  For.  Quar- 
terly, 14:  4:  578-588,  Dec.  1916. 

Mattoon,  Wilbur  R.:  The  Slash  Pine.  Amer.  For.,  23:279:158-160; 
Mch.  1917. 

nPinus  palustris: 

Koehler,  Arthur:  A  Visual  Method  of  Distinguishing  Longleaf  Pine. 
Amer.  Lumberman,  Sept.  11,  1915,  pp.  34-35. 

Fernow,  B.  E.:  Timber  Physics.  Part  II.:  Results  of  Investigations  on 
Longleaf  Pine.     Bui.  8,  U.  S.  Div.  Forestry,  1893. 

Bitting,  Katherine  G. :  The  Histological  Difference  between  Pinus  tceda 
and  Pinus  palustris.  Proc.  Ind.  Acad.  Sci.,  Indianapolis,  Ind.,  1908,  pp.  127- 
129. 

Buttrick,  P.  L.:  Commercial  Uses  of  Longleaf  Pine.  Amer.  For., 
21:  261:  896-908,  Sept.  1915. 

nPinus  tceda: 

Ashe,  W.  W.:  Loblolly  or  North  Carolina  Pine.  Bui.  24,  N.  C.  Geol.  and 
Econ.  Survey,  1915. 

Sterrett,  W.  |D.:  Forest  Management  of  Loblolly  Pine  in  Delaware, 
Maryland,  and  Virginia.     Bui.  11,  U.  S.  Forest  Service,  1914. 

Zon,  Raphael:  Loblolly  Pine  in  Eastern  Texas.  Bui.  64,  U.  S.  Forest 
Service,  1905. 

Hatt,  W.  Kendrick:  Second  Progress  Report  on  the  Strength  of  Structural 
Timber.     Cir.  115,  U.  S.  Forest  Service,  1907. 

lzPinus  echinata: 

Mattoon,  Wilbur  R.:  Shortleaf  Pine:  Its  Economic  Importance  and 
Forest  Management.     Bui.  308,  U.  S.  Forest  Service,  1915. 

Mattoon,  Wilbur  R.:  Life  History  of  Shortleaf  Pine.  Bui.  244,  U.  S. 
Forest  Service,  1915. 

Detwiler,  Samuel  B.:  Shortleaf  Pine.  Amer.  For.,  22:273:513-520. 
Sept.  1916. 

uPseudolsuga: 

Cline,  McGarvey,  and  Knapp,  J.  B.:  Properties  and  Uses  of  Douglas  Fir. 
Bui.  88,  U.  S.  Forest  Service,  1911. 

Detwiler,  Samuel  B.:  Douglas  Fir.  Amer.  For.,  22:  266:  67-75,  Feb. 
1916. 

Frothingham,  E.  H. :  Douglas  Fir:  A  Study  of  the  Pacific  Coast  and  Rocky 
Mountain  Forms.     Cir.  150,  U.  S.  Forest  Service,  1909. 


ECONOMIC   WOODS   OF    THE   UNITED   STATES  111 

Knapp,  Joseph  B.:  Fire-killed  Douglas  Fir:  A  Study  of  Its  Rate  of  De- 
terioration, Usability,  and  Strength.     Bui.  112,  U.  S.  Forest  Service,  1912. 

Lee,  H.  N.:  Canadian  Woods  for  Structural  Timbers.  Bui.  59,  For. 
Branch,  Dept.  Int.,  Canada,  1917. 

Record,  Samuel  J.:  Douglas  Fir.  Amer.  Architect,  112:  2195:  329-333, 
Nov.  7,  1917. 

15Larch: 

Ross,  A.  H.  D.:  Commercial  Importance  of  Tamarack.  Can.  Lumberman 
and  Woodworker,  35: 15:  36-37,  Aug.  1,  1915. 

uSpruce: 

Sudworth,  George  B.:  The  Spruce  and  Balsam  Fir  Trees  of  the  Rocky 
Mountain  Region.     Bui.  327,  U.  S.  Forest  Service,  1910. 

Hodson,  E.  R.,  and  Foster,  J.  H.:  Engelmann  Spruce  in  the  Rocky 
Mountains.     Cir.  170,  U.  S.  Forest  Service,  1910. 

Jeffrey,  Edward  C:  The  Comparative  Anatomy  and  Phylogeny  of  the 
Coniferales.     Part  II,  Abietinese.     Mem.  Boston  Soc.  Nat.  His.,  6:  1,  1905. 

Bastin,  E.  S.,  and  Trimble,  H. :  A  Contribution  to  the  Knowledge  of  North 
American  Coniferae.     Amer.  Journ.  Pharm.,  68:  8:  409-422,  1896. 

vPicea  rubens: 

Buttrick,  P.  L.:  The  Red  Spruce.  Amer.  For.,  22:276:705-711,  Dec. 
1916. 

Murphy,  Louis  S.:  The  Red  Spruce:  Its  Growth  and  Management.  Bui. 
544,  U.  S.  Dept.  Agr.,  1917. 

lsFir: 

Sudworth,  George  B.:  The  Spruce  and  Balsam  for  Trees  of  the  Rocky 
Mountain  Region.     Bui.  327,  U.  S.  Forest  Service,  1916. 

Thompson,  W.  P.:  Ray  Tracheids  in  Abies.  Bot.  Gaz.,  53:4:331-338, 
Apr.  1912. 

^Hemlock: 

Ross,  A.  H.  D.:  The  Commercial  Importance  of  Hemlock.  Can.  Lumber- 
man and  Woodworker,  35:  12:  32-33,  June  15,  1915. 

xTsuga  helerophylla: 

Hanzlik,  Edward  J.,  and  Oakleaf,  Howard  B.:  Western  Hemlock:  Its 
Forest  Characteristics,  Properties  and  Uses.  Timberman,  Portland,  Ore., 
Oct.  1914. 

Allen,  Edward  T. :  The  Western  Hemlock.     Bui.  33,  U.  S.  Bur.  For.,  1902. 

Oakleaf,  Howard  B. :  Wood-using  Industries  of  Oregon.  Pub.  by  Oregon 
Cons.  Assn.,  Portland,  Ore.,  1911,  pp.  29-30. 

21Sequoia: 

Detwiler,  Samuel  B.:  The  Redwoods.  Amer.  For.,  22:270:323-332, 
June  1916. 

Hall,  William  R.,  and  Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the 
United  States.  I.  Cedars,  Cypresses,  and  Sequoias.  Bui.  95,  U.  S.  Forest 
Service,  1911,  pp.  57-62. 

Jeffrey,  Edward  C:  The  Comparative  Anatomy  and  Phylogeny  of  the 
Coniferales.  Part  I,  The  Genus  Sequoia.  Mem.  Boston  Soc.  Nat.  His., 
5:  10: 441-459. 


112  ECONOMIC    WOODS   OF   THE    UNITED   STATES 

Jeffrey,  Edward  C:  A  Fossil  Sequoia  from  the  Sierra  Nevada.  Bot. 
Gaz.,  38:  5:  321-332,  Nov.  1904. 

^Sequoia  washingtoniana: 

A  Short  Account  of  the  Big  Trees  of  California.     Bui.  28,  U.  S.  Div.  For., 
1910. 
^Sequoia  semper  vir  ens: 

Fisher,  Richard  T.,  el  al:  The  Redwood.     Bui.  38,  U.  S.  Bur.  For.,  1903. 

Gordon,  Marjorie:  Ray  Tracheids  in  Sequoia  sempervirens.  New. 
Phytologist,  11:  1:  1-7,  Jan.  1912. 

nTaxodium: 

Mattoon,  Wilbur  R.:  Southern  Cypress.  Bui.  272,  U.  S.  Forest  Service, 
1915. 

Record,  Samuel  J.:  The  Southern  Cypress.  Amer.  Architect,  Oct.  18, 
1916,  pp.  247-254. 

Detwiler,  Samuel  B. :  The  Bald  Cypress.  Amer.  For.,  22:  274:  577-585, 
Oct.  1916. 

Roth,  Filibert:  Progress  in  Timber  Physics:  Bald  Cypress  (Taxodium 
distichum).     Cir.  19,  U.  S.  Div.  For.,  1898. 

Hall,  William  R.,  and  Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the 
United  States.  I.  Cedars,  Cypresses,  and  Sequoias.  Bui.  95,  U.  S.  Forest 
Service,  1911,  pp.  41-47. 

^Cedar  Group: 

Hall,  William  R.,  and  Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the 
United  States.  I.  Cedars,  Cypresses,  and  Sequoias.  Bui.  95,  U.  S.  Forest 
Service,  1911,  pp.  11-40. 

Ross,  A.  H.  I).:  The  Commercial  Importance  of  Cedar.  Can.  Lumber- 
man and  Woodworker,  35:  13:  28-28,  July  1,  1915. 

™Libocedrus: 

Mitchell,  J.  Alfred:  Incense  Cedar.     Bui.  No.  640,  U.  S.  Dept.  Agr., 
1918. 
vjuniperus: 

Mohr,  Charles:  Notes  on  the  Red  Cedar.     Bui.  31,  U.  S.  Bur.  For.,  1901. 

White,  L.  L. :  Production  of  Red  Cedar  for  Pencil  Wood.  Cir.  102,  U.  S. 
Forest  Service,  1907. 

2SThuya  plicata: 

Knapp,  Joseph  B.,  and  Jackson,  Alexander  G.:  Western  Red  Cedar  in 
the  Pacific  Northwest.  West  Coast  Lumberman,  Seattle-Tacoma,  Feb.  1  and 
Mch.  1,  1914. 

Detwiler,  Samuel  B.:  Western  Red  Cedar.  Amer.  For.,  22:  267: 131- 
137,  Mch.  1916. 

Flavelle,  Aird:  British  Columbia  Red  Cedar.  Can.  Lumberman  and 
Woodworker,  35:  20:  30-32,  Oct.  15,  1915. 

™Castanea: 

Murdock,  John,  Jr.:  Chestnut:  Its  Market  in  Massachusetts.  Pub. 
State  Forester  of  Mass.,  Boston,  1912. 

Detwiler,  Samuel  B.:  The  American  Chestnut  Tree.  Amer.  For., 
21:262:957-960,  Oct.  1915. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  113 

Buttrick,  P.  L. :  Commercial  Uses  of  Chestnut.  Amer.  For.,  21 :  262:  960- 
967,  Oct.  1915. 

Buttrick,  P.  L.:  Chestnut  as  a  Pulp  Wood.     Pulp  and  Paper  Mag.,  Nov. 

I,  1915,  pp.  554-5. 

Ashe,  W.  W.:  Chestnut  in  Tennessee.  Bui.  10,  B,  Tenn.  Geol.  Survey, 
Nashville,  1912. 

Zon,  Raphael:  Chestnut  in  Southern  Maryland.  Bui.  53,  U.  S.  Bur.  For., 
1904. 

Lavaille,  J.  B.:  Le  Chataignier,  Paris,  1906. 

™Oak: 

Sudworth,  George  B.,  and  Mell,  C.  D.:  The  Identification  of  Important 
North  American  Oak  Woods.     Bui.  102,  U.  S.  Forest  Service,  1911. 

Record,  Samuel  J.:  An  Easy  Identification  of  the  Oaks.  Hardwood 
Record,  Dec.  25,  1914,  p.  23. 

Ross,  A.  H.  D.:  The  Commercial  Importance  of  Oak.  Can.  Lumberman 
and  Woodworker,  35:  17:  28-30,  Sept.  1,  1915. 

Bailey,  Irving  W.:  Notes  on  the  Wood  Structure  of  the  Betulaceae 
and  Fagacese.     For.  Quarterly,  8:  2:  178-190,  June  1910. 

Bailey,  Irving  W. :  On  the  Origin  of  the  Broad  Ray  in  Quercus.  Bot.  Gaz., 
49:3:161-167,  Mch.  1910. 

Bailey,  Irving  W.:  Reversionary  Characters  of  Traumatic  Oak  Woods. 
Bot.  Gaz.,  50:  5:  374-380,  Nov.  1910. 

Groom,  Percy:  The  Evolution  of  the  Annual  Ring  and  Medullary  Rays  of 
Quercus.     Annals  of  Botany,  25:  983-1004,  Oct.  1911. 

Abromeit,  Johannes:  Ueber  die  Anatomie  des  Eichenholzes.  Berlin, 
1884. 

zlQuercus  alba: 

Greeley,  W.  B.,  and  Ashe,  W.  W.:  White  Oak  in  the  Southern  Appala- 
chians.    Cir.  105,  U.  S.  Forest  Service,  1907. 

Langdon,  LaDema  M.:  The  Ray  System  of  Quercus  alba.  Bot.  Gaz., 
65:4:313-323,  Apr.  1918. 

Detwiler,  Samuel  B.:  The  American  White  Oak.     Amer.  For.,  22:  265:  3- 

II,  Jan.  1916. 

3-Quercus  prinus: 

Foster,  H.  D.,  and  Ashe,  W.  W.:  Chestnut  Oak  in  the  Southern  Appa- 
lachians.    Cir.  135,  U.  S.  Forest  Service,  1906. 

33Elm: 

Brush,  W.  D.:  Utilization  of  Elm.     Bui.  No.  683,  U.  S.  Dept.  Agr.,  1918. 

Record,  Samuel  J.:  The  Wood  of  the  Elms.  Barrel  and  Box,  Nov.  10, 
1912,  p.  33. 

3iUlmus  americana: 

Detwiler,  Samuel  B.:  The  American  Elm.  Amer.  For.,  22:269:  259- 
267,  May  1916. 

^Ulmus  racemosa: 

Frothingham,  E.  H.:  Rock  Elm.  Journ.  Forestry,  16:  7:  834-836.  Nov.; 
16:  8:  950,  Dec.  1918. 


114  ECONOMIC   WOODS    OF   THE   UNITED    STATES 

**Toxylon: 

Maxwell,  Hu:  Utilization  of  Osage  Orange.  Pub.  Farm  Wagon  Dept., 
Natl.  Implement  and  Vehicle  Assn.,  U.  S.  A.,  1911. 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  Fustic  Wood:  Its  Sub- 
stitutes and  Adulterants.     Cir.  184,  U.  S.  Forest  Service,  1911,  pp.  8-9. 

Kressman,  F.  W.:  Osage  Orange:  Its  Value  as  a  Commercial  Dyestuff. 
Journ.  Ind.  and  Eng.  Chem.,  6:6.  462-464,  June  1914. 

31Robinia: 

Detwiler,  Samuel  B.:  The  Locusts:  Identification  and  Characteristics. 
Amer.  For.,  23:  278:  88-93,  Feb.  1917. 

Record,  Samuel  J.:  Some  Woods  of  the  Pea  Family.  Hardwood  Record, 
Mch.  25,  1913,  pp.  28-29. 

Jaensch,  Th.:  Zur  Anatomie  einiger  Leguminosenholzer.  Ber.  d.  deut- 
schen  Bot.  Gesellschaft,  Vol.  II,  Berlin,  1884. 

Saupe,  K.  Alwin:  Der  Anatomische  Bau  des  Holzes  der  Leguminosen  und 
sein  Systematischenwerth.  Regensburg,  1887. 

Vadas,  Engen.:  Beitrage  zur  Anatomie  des  Robinienholzes.  Natur. 
Zeitsch.  f.  L.-  u.  Forstw.,  1905,  303-308. 

3SProsopis: 

Forbes,  R.  H.:  The  Mesquite  Tree:  Its  Products  and  Uses.  Bui.  No.  13, 
Ariz.  Agr.  Exp.  Sta.,  Tucson,  1895. 

Maxwell,  Hu  and  Hatch,  Charles  F.:  Wood-using  Industries  of  Texas. 
Lumber  Trade  Journ.,  New  Orleans,  June  15,  1912,  pp.  31-32. 

39Sassafras: 

Knoblauch,  E.:  Anatomie  des  Holzes  der  Laurineen.  Flora,  22-26:  339- 
400,  1888. 

^Catalpa: 

Hall,  William  L.:  The  Hardy  Catalpa.     Bui.  37,  U.  S.  Bur.  For.,  1902. 

Roberts,  H.  F.:  The  Hardy  Catalpa.  Bui.  No.  108,  Exp.  Sta.,  Kansas 
State  Agr.  Col.,  Manhattan,  1902. 

Record,  Samuel  J. :  The  Hardy  Catalpa.  Pub.  22,  Dept.  Botany,  Wabash 
College,  Crawfordsville,  Ind.,  1906. 

"Ash: 

Sterrett,  W.  D.:  The  Ashes:  Their  Characteristics  and  Management. 
Bui.  No.  299,  U.  S.  Dept.  Agr.,  1915. 

Sterrett,  W.  D.:  Utilization  of  Ash.  Bui.  No.  523.  U.  S.  Dept.  Agr., 
1917. 

Record,  Samuel  J. :  The  Wood  of  the  Ashes.  Hardwood  Record,  Nov.  10, 
1912,  pp.  28-29. 

^Fraxinus  americana: 

Detwiler,  Samuel  B.:  White  Ash.  Amer.  For.,  21 :  264:  1081-1089,  Dec. 
1915. 

izDiospyros: 

Molisch,  H.:  Vergleichende  Anatomie  des  Holzes  der  Ebenaceen  und  ihrer 
Verwandten.     Sitz.  d.  kaiserl.  Akad.  d.  Wissenschaft,  80,  Pt.  1,  Wien,  1879. 

Record,  Samuel  J.:  Persimmon:  Its  Uses  and  Its  Substitutes.  Sou. 
Lumberman,  Dec.  25,  1912,  pp.  95-96. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  115 

Fletcher,  W.  F. :  The  Native  Persimmon.  Farmers'  Bui.  685,  U.  S.  Dent. 
Agr.,  1915. 

^Hickory: 

Boisen,  Anton  T.,  and  Newlin,  J.  A.:  The  Commercial  Hickories.  Bui. 
80,  U.  S.  Forest  Service,  1910. 

Hatch,  Charles  F.:  Manufacture  and  Utilization  of  Hickory,  1911.  Cir. 
187,  U.  S.  Forest  Service,  1911. 

Detwiler,  Samuel  B.:  The  Hickories.  Amer.  For.,  22:272:451-457, 
Aug.  1916. 

^Walnut: 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  Identification  of  North 
American  Walnut  Woods.     Hardwood  Record,  Sept.  10  and  25,  1914. 

Record,  Samuel  J.:  The  Walnuts  and  the  Hickories.  Hardwood  Record, 
Apr.  25,  1913,  pp.  27-29. 

KSwietenia: 

Mell,  C.  D.:  True  Mahogany.     Bui.  No.  474,  U.  S.  Dept.  Agr.,  1917. 

Record,  Samuel  J.:  Mahogany  and  Some  of  Its  Substitutes.  Journ. 
Forestry,  17:  1: 1-8,  Jan.  1919. 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  "Colombian  Ma- 
hogany": Its  Characteristics  and  Its  Use  as  a  Substitute  for  True  Mahogany. 
Cir.  185,  U.  S.  Forest  Service,  1911. 

Busch,  P.:  The  Commercial  Mahoganies.  Tropenpflanzen.  15:9:479- 
493,  1911. 

Dixon,  Henry  H. :  Mahogany,  and  the  Recognition  of  Some  of  the  Differ- 
ent Kinds  by  Their  Microscopic  Characteristics.  Sci.  Proc,  Royal  Dublin 
Soc,  15  (n.  s):  34:  431-486,  Dec.  1918. 

A"' 'Eucalyptus: 

Betts,  H.  S.,  and  Smith,  C.  Stowell:  Utilization  of  California  Eucalypts. 
Cir.  179,  U.  S.  Forest  Service,  1910. 

.  Tiemann,  H.  D.:  Eucalyptus  Lumber.     Hardwood  Record,  Sept.  25  and 
Oct.  10,  1913. 

Woodbury,  T.  D.:  Yield  and  Returns  of  Blue  Gum  in  California.  Cir. 
210,  U.  S.  Forest  Service,  1912. 

^Evergreen  Oaks: 

Bailey,  Irving  W.:  Notes  on  the  Wood  Structure  of  the  Betulaceae  and 
Fagaceae.     For.  Quarterly,  8:2:  178-185,  June  1910. 

Sudworth,  George  B.,  and  Mell,  C.  D.:  The  Identification  of  Important 
American  Oak  Woods.     Bui.  102,  U.  S.  Forest  Service,  1912. 

i9Quercus  densiflora: 

Jepson,  Willis  Linn,  and  Betts,  H.  S.:  California  Tanbark  Oak.  Bui. 
75,  U.  S.  Forest  Service,  1911. 

50Carpinus: 

Bailey,  Irving  W.:  Notes  on  the  Wood  Structure  of  the  Betulaceae  and 
Fagaceae.     For.  Quarterly,  8:  2:  178-185,  June  1910. 

blPlatanus: 

Brush,  Warren  D.:  Distinguishing  Characteristics  of  North  American 
Sycamore  Woods.     Bot.  Gaz.,  64:  6:  480-496,  Dec.  1917. 


PROPl 

1/eg* 


116  ECONOMIC   WOODS   OF   THE   UNITED   STATES 

62Fagus: 

Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the  United  States.  Beech,, 
Birches,  and  Maples.     Bui.  No.  12,  U.  S.  Forest  Service,  1913. 

^Maple: 

Maxwell,  Hu:  Loc  cU. 

Record,  Samuel  J.:  Differentiating  Between  Maples.  Hardwood  Record,. 
July  10,  1913,  pp.  26-27. 

Ross,  A.  H.  D.:  Commercial  Importance  of  Maple.  Can.  Lumberman  and 
Woodworker,  35:  18:  36-37,  Sept.  15,  1915. 

Holden,  Ruth:  Some  Features  in  the  Anatomy  of  the  Sapindales.  Bot. 
Gaz.,  53:  1:  50-57,  Jan.  1912. 

MAcer  saccharum: 

Maxwell,  Hu:  Commercial  Uses  of  Sugar  Maple.  Amer.  For., 
21:  263:  1022-1030,  Nov.  1915. 

65Birch: 

Maxwell,  Hu  :  Uses  of  Commercial  Woods  of  the  United  States.  Beech, 
Birches,  and  Maples.     Bui.  No.  12,  U.  S.  Forest  Service,  1913. 

Detwiler,  Samuel  B.:  The  Birches.  Amer.  For.,  22:  268:  195-201,  Apr. 
1916. 

Record,  Samuel  J.:  The  Wood  of  the  Birches.  Hardwood  Record,  Oct. 
25,  1912,  pp.  32-33. 

seBetula  papyrifera: 

Dana,  S.  T. :  Paper  Birch  in  the  Northeast.  Cir.  163,  U.  S.  Forest  Service,. 
1909. 

67Apple: 

Record,  Samuel  J.:  Making  Hand-saw  Handles.  Wood  Worker,  In- 
dianapolis, 31:  10:  37-38,  Dec.  1912. 

^Liquidambar: 

Chittenden,  Alfred  K.,  and  Hatt,  W.  Kendrick:  The  Red  Gum.  Bui. 
58,  U.  S.  Bur.  For.,  1905. 

Record,  Samuel  J.:  Red  Gum.  American  Architect,  Apr.  19,  1916;  also 
Decorative  Furnisher.  30:  4:  42-44,  54,  July  1916. 

Detwiler,  Samuel  B.:  The  Red  Gum.  Amer.  For.,  22: 275:  641-647,  Nov. 
1916. 

mNyssa: 

Holroyd,  H.  B.:  The  Utilization  of  Tupelo.  Cir.  40,  U.  S.  Forest  Service, 
1906. 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  Distinguishing  Char- 
acteristics of  North  American  Gumwoods.  Bui.  103,  U.  S.  Forest  Service,. 
1911. 

Von  Schrenk,  Hermann  :  Tupelo.  Sou.  Lumberman,  Anniv.  Ed.,  1907. 
*°Liriodendron: 

The  Tulip  or  Yellow  Poplar  Tree.     Amer.  For.,  21:8:  833-840,  Aug.  1915. 

Groppler,  Robert:  Vergleichended  Anatomie  des  Holzes  der  Magnolia- 
ceen.     Stuttgart,  1894.     See  also  Bot.  Centralblatt,  60:  373. 


ECONOMIC   WOODS    OF   THE    UNITED   STATES  117 

61-62Tilia,  Aesculus: 

Record,  Samuel  J.:  Tier-like  Arrangement  of  the  Elements  of  Certain 
Woods.     Science,  34:  75-77,  Jan.  12,  1912. 

*3Alnus: 

Bailey,  Irving  W.:  The  Relation  of  the  Leaf -trace  to  the  Formation  of 
Compound  Rays  in  the  Lower  Dicotyledons.  Annals  of  Botany,  25:  97:  225- 
241,  Jan. 1911. 

Oakleaf,  Howard  B.:  The  Wood-using  Industries  of  Oregon.  Pub. 
Oregon  Conservation  Assn.,  1911. 

6iSalix: 

Penhallow,  D.  P. :  A  Systematic  Study  of  the  Salicacese.  Am.  Naturalist, 
39:464,  Aug.  1905. 

Lamb,  George  N.:  Willows:  Their  Growth,  Use,  and  Importance.  Bui. 
316,  U.  S.  Forest  Service,  1915. 

Detwiler,  Samuel  B.:  The  Willows:  Identification  and  Characteristics. 
Amer.  For.,  23:  277:  3-10,  Jan.  1917. 

Holden,  Ruth:  Reduction  and  Reversion  in  the  North  American  Salicales. 
Annals  of  Botany,  26:  165-173,  Jan.  1912. 

^Populus: 

Williamson,  A.  W.:  Cottonwood  in  the  Mississippi  Valley.  Bui.  No.  24, 
U.  S.  Forest  Service,  1913. 

Burgerstein,  A. :  Diagnostische  Merkmale  der  Markstrahlen  von  Populus 
und  Salix.     Ber.  d.  deut.  bot.  Gesellschaft,  29,  Nov.  10,  1911. 

Breton-Bonnard,  L.:  Le  Peuplier.  Paris,  Lucien  Laveur,  1903. 
**Aspen: 

Weigle,  W.  G.,  and  Frothingham,  E.  H.:  The  Aspens:  Their  Growth  and 
Management.     Bui.  93,  U.  S.  Forest  Service,  1911. 


BIBLIOGRAPHY 

I.  Woods  in  General 

Abromeit,  Johannes:  Ueber  die  Anatomie  des  Eichenholzes.  Berlin,  G. 
Bernstein,  1884. 

Boulger,  G.  S.:  Wood:  A  Manual  of  the  Natural  Histories  and  Industrial 
Applications  of  the  Timbers  of  Commerce  (2d  ed.).  London,  Edward  Arnold, 
1908. 

Charpentier,  Paul:  Timber:  A  Comprehensive  Study  of  Wood  in  All  its 
Aspects  (trans,  from  the  French  by  Joseph  Kennell).  London,  Scott,  Green- 
wood &  Co.,  1902. 

DeBary,  A.:  Comparative  Anatomy  of  the  Vegetative  Organs  of  the 
Phanerogams  and  Ferns  (English  edition),  Oxford,  1884,  pp.  495-496.  (Classi- 
fication condensed  from  Sanio) . 

Gayer,  Karl:  Forest  Utilization  (Vol.  5  of  Schlich's  Manual  of  Forestry; 
trans  from  the  German  by  W.  R.  Fisher;  2d  ed.).  London,  Bradbury,  Agnew 
&  Co.,  1908. 

Hanausek,  T.  F.:  The  Microscopy  of  Technical  Products  (English  edition), 
New  York,  1907. 

Hartig,  Th.:  Anatomie  und  Physiologie  der  Holzpflanzen.  Berlin,  Julius 
Springer,  1878. 

Hubert,  E.:  Le  Bois  et  le  Liege,  Paris,  J.  B.  Bailliere  &  Sons,  1902. 

Jaccard,  P.:  fitude  Anatomique  de  Bois  comprimes,  Zurich,  Switzerland, 
F.  Lohbauer,  1910. 

Jeffrey,  Edward  C:  The  Anatomy  of  Woody  Plants.  Chicago,  Univ.  of 
Chicago  Press,  1917. 

Jones,  W.  S.:  The  Structure  of  the  Timbers  of  Some  Common  Genera  of 
Coniferous  Trees.     Quar.  Journ.  Forestry,  6:  2:  112-134,  Apr.  1912. 

Kottmeier,  H.,  and  Uhlmann,  F. :  Das  Holz.  Leipzig,  Quelle  &  Meyer, 
1910. 

Krais,  Paul:  Gewerbliche  Materialkunde :  Die  Holzer.  Stuttgart,  Felix 
Krais,  1910. 

Laris,  E.:  Rohholzgewinnung  und  Gewerbseigenschaften  des  Holzes. 
Vienna  and  Leipzig,  1909. 

Laslett,  Thomas:  Timber  and  Timber  Trees,  Native  and  Foreign  (2d  ed.; 
revised  and  enlarged  by  H.  Marshall  Ward).  London  and  New  York,  Mac- 
millan  &  Co.,  1894. 

Note.  —  For  publications  referring  to  species  listed  in  the  Key  see  list  of 
references,  pp.  109  to  117. 

119 


120  ECONOMIC   WOODS    OF   THE   UNITED   STATES 

Mackenzie,  D.  F.:  The  Identification  of  Timber;  with  a  Uniform  Series 
of  Photo-micrographs.  Trans.  Highland  and  Agr.  Soc.  of  Scotland,  Ser.  5, 
Vol.  12,  pp.  183-224,  1900. 

Mathey,  Alphonse:  Traite  d'Exploitation  Commerciale  des  Bois.  Vols. 
1-2.     Paris,  Lucien  Laveur,  1908. 

Muller,  N.  J.  C:  Atlas  der  Holzstructur.  Halle  A.  S.,  Wilhelm  Knapp, 
1888. 

Sanio,  Carl:  Vergleichende  Untersuchungen  uber  des  Holzkorpers,  Bot. 
Zeit.,  21:51:401-8,  1863. 

Schacht,  Hermann:  Der  Baum.  Studien  iiber  Bau  und  Leben  der 
hoheren  Gewachse.     Berlin,  G.  M.  F.  Muller,  1853. 

Schroeder,  Julius:  Das  Holz  der  Coniferen.     Dresden,  1872. 

Schwartz,  T.:  Forstliche  Botanik.     Berlin,  1892. 

Solereder,  Hans:  Systematic  Anatomy  of  the  Dicotyledons.  Vols.  1-2. 
(English  edition),  Oxford,  Clarendon  Press,  1908. 

Stephenson,  William:  The  Trees  of  Commerce  (rev.  ed.).  London,  W. 
Ryder  &  Son,  1908. 

Stone,  Herbert:  The  Timbers  of  Commerce  and  Their  Identification. 
London,  W.  Ryder  &  Son,  1904. 

Wiesner,  Julius:  Die  Rohstoffe  des  Pflanzen  Reiches.  Vol.  2.  Leipzig, 
Wilhelm  Engelmann,  1903. 

Wilda,  Hermann:  Das  Holz:  Aufbau,  Eigenschaften  und  Verwendung. 
Leipzig,  G.  J.  Goschen,  1910. 

II.   Woods  of  United  States  and  Canada 
1.   Miscellaneous 

Ashe,  W.  W.:  Loblolly  or  North  Carolina  Pine,  N.  C.  Geol.  and  Ecoru 
Survey  Bui.  No.  24,  Raleigh,  N.  C,  1915. 

Bailey,  Irving  W.:  The  Role  of  the  Microscope  in  the  Identification  and 
Classification  of  the  "Timbers  of  Commerce."  Journ.  of  Forestry,  5:  12:  176- 
191,  Feb.  1917. 

Bastin,  Edson  S.  and  Trimble,  Henry:  A  Contribution  to  the  Knowledge 
of  the  North  American  Coniferae.  Reprint,  Am.  Journ.  Pharm.,  Vols.  68-69, 
1896-7. 

Baterden,  J.  R.:  Timber.     New  York,  D.  Van  Nostrand  &  Co.,  1908. 

Betts,  H.  S.,  and  Greeley,  W.  B.:  Structural  Timber  in  the  United  States. 
International  Engineering  Congress,  San  Francisco,  Cal.,  1915. 

British  Columbia  Western  Soft  Pine.  Bui.  17,  British  Columbia, 
Forest  Branch.     Victoria,  1916. 

Britton,  N.  L.:  North  American  Trees.  New  York,  Henry  Holt  &  Co., 
1906. 

Burns,  G.  P.  and  Otis,  C.  H.:  The  Trees  of  Vermont.  Contains:  "The 
Structure  and  Identification  of  Our  Common  Lumber  Woods"  by  C.  H.  Otis, 
pp.  194-232.     Bui.  No.  194,  Vermont  Agr.  Exp.  Sta.,  Burlington,  Vt.,  1916. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  121 

Dickerson,  Cynthia:  Trees  and  Forestry:  An  Elementary  Treatment  of 
the  Subject  Based  on  the  Jesup  Collection  of  North  American  Woods  in  the 
American  Museum  of  Natural  History.  Pub.  by  the  Museum,  New  York> 
1910. 

Elliott,  S.  B. :  The  Important  Timber  Trees  of  the  United  States.  Boston 
and  New  York,  Houghton  Mifflin  Co.,  1912. 

Gibson,  Henry  H.,  and  Maxwell,  Hu:  American  Forest  Trees.  Chicago, 
Hardwood  Record,  1913. 

Hough,  Franklin  B.:  The  Elements  of  Forestry.  Cincinnati,  The  Robert 
Clarke  Co.,  1898. 

Hough,  Romeyn  B.:  American  Woods  (Sections  and  Text).  Vols.  1-13, 
Lowville,  N.  Y.,  the  author,  1893-1913. 

Hough,  Romeyn  B.:  Handbook  of  the  Trees  of  the  Northern  States  and 
Canada  East  of  the  Rocky  Mountains.     Lowville,  N.  Y.,  the  author,  1907. 

Koehler,  Arthur:  Guidebook  for  the  Identification  of  Woods  used  for 
Ties  and  Timbers.     U.  S.  Forest  Service,  Washington,  D.  C,  1917. 

Jepson,  Willis  L.:  The  Silva  of  California  (Vol.  II,  Memoirs  of  the  Uni- 
versity of  California).     Berkeley,  University  Press,  1910. 

Lazenby,  William  R.:  Qualities  and  Uses  of  the  Woods  of  Ohio.  Bui.  6, 
Ohio  Biol.  Survey.     Columbus,  O.,  1916. 

Lee,  H.  N.:  Canadian  Woods  for  Structural  Timbers.  Dept.  of  Int., 
Canada.     Forestry  Branch,  Bid.  No.  59,  Ottawa,  1917. 

Levison,  J.  J. :  Studies  of  Trees.    New  York,  John  Wiley  &  Sons,  Inc.,  1914. 

Mohr,  Charles,  and  Roth,  Filibert:  The  Timber  Pines  of  the  Southern 
United  States,  together  with  a  Discussion  of  the  Structure  of  their  Wood. 
Bui.  13  (rev.  ed.)  U.  S.  Div.  Forestry,  Washington,  D.  C,  1897. 

Newlin,  J.  A.,  and  Wilson,  Thomas  R.  C:  Mechanical  Properties  of 
Woods  Grown  in  the  United  States.  Bui.  No.  556,  U.  S.  Dept.  Agr.,  Wash- 
ington, D.  C,  1917. 

Noyes,  William:  Wood  and  Forest  (2d  ed.).  The  Manual  Arts  Press, 
Peoria,  111.,  1911. 

Pexhallow,  David  P.:  A  Manual  of  the  North  "American  Gymnosperms, 
exclusive  of  the  Cycadales,  but  together  with  Certain  Exotic  Species.  Boston, 
Ginn  &  Co.,  1907. 

Pinchot,  Gifford,  and  Ashe,  W.  W. :  Timber  Trees  and  Forests  of  North 
Carolina.     Bui.  6,  N.  C.  Geol.  Survey,  Chapel  Hill,  N.  C,  1897. 

Prichard,  R.  P. :  The  Structure  of  the  Common  Woods  of  New  York  and 
the  Wood  Collection.  Bui.  N.  Y.  State  College  of  Forestry,  Syracuse,  N.  Y., 
March  1915. 

Rattinger,  K.  K.:  Die  Nutzholzer  der  Vereinigten  Staaten;  I.  Die  Nadel- 
holzer.    Wiesbaden,  Verlag  Forstburo,  1910. 

Record,  Samuel  J.:  The  Mechanical  Properties  of  Wood.  New  York, 
John  Wiley  &  Sons,  Inc.,  1914. 

Roth,  Filibert:  Timber:  An  Elementary  Discussion  of  the  Characteristics 
and  Properties  of  Woods.  Bui.  No.  10,  U.  S.  Div.  of  Forestry,  Washington, 
D.  C,  1895. 


122  ECONOMIC   WOODS    OF   THE   UNITED    STATES 

Sargent,  Chas.  S. :  Report  on  the  Forests  of  North  America  (exclusive  of 
Mexico).     Vol.  9,  Tenth  Census,  Washington,  D.  C,  1884. 

Sargent,  Chas.  S. :  The  Woods  of  the  United  States,  with  an  Account  of 
the  Structure,  Qualities  and  Uses  (Jesup  Collection).  New  York,  D.  Appleton 
A  Co.,  1885. 

1  Sargent,  Chas.  S.:  The  Silva  of  North  America:  A  Description  of  the 
Trees  which  Grow  Naturally  in  North  America,  exclusive  of  Mexico.  Vols. 
1-14.     Boston  and  New  York,  Houghton  Mifflin  Co.,  1891-1902. 

Sargent,  Chas.  S.:  Manual  of  the  Trees  of  North  America  (exclusive  of 
Mexico).     Boston  and  New  York,  Houghton  Mifflin  Co.,  1905. 

Shinn,  Charles  H. :  Economic  Possibilities  of  Pinus  sabiniana.  Proc.  Soc. 
Am.  Foresters,  6: 1:  68-77,  1911. 

Snow,  Charles  H.:  The  Principal  Species  of  Wood  (2d  ed.).  New  York, 
John  Wiley  &  Sons,  Inc.,  1908. 

Snow,  Charles  H.:  Wood  and  Other  Organic  Structural  Materials.  New 
York,  McGraw-Hill  Book  Co.,  1917. 

Southern  Yellow  Pine  Timbers.  Including  Definition  of  the  New 
"Density"  Rule.  Adopted  and  copyrighted  by  the  American  Society  for 
Testing  Materials.  Approved  and  adopted  by  the  Southern  Pine  Association 
of  New  Orleans,  La.,  Nov.  1915. 

Sterrett,  W.  D. :  Scrub  Pine.  Bui.  94,  U.  S.  Forest  Service,  Washington, 
D.  C,  1911. 

Sudworth,  George  B.:  Forest  Trees  of  the  Pacific  Slope.  U.  S.  Forest 
Service,  Washington,  D.  C,  1908. 

Sudworth,  George  B.:  Miscellaneous  Conifers  of  the  Rocky  Mountain 
Region.     Bui.  No.  680,  U.  S.  Dept.  Agr.,  Washington,  D.  C,  1918. 

Sudworth,  George  B.:  The  Pine  Trees  of  the  Rocky  Mountain  Region. 
Bui.  No.  460,  U.  S.  Dept.  Agr.,  Washington,  D.  C,  1917. 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  The  Identification  of 
Important  North  American  Oak  Woods,  based  on  a  Study  of  the  Secondary 
Wood.     Bui.  102,  U.  S.  Forest  Service,  Washington,  D.  C,  1911. 

Sudworth,  George  B.,  and  Mell,  Clayton,  D.:  Distinguishing  Char- 
acteristics of  North  American  Gumwoods,  based  on  the  Anatomy  of  the 
Secondary  Wood.     Bui.  103,  U.  S.  Forest  Service,  Washington,  D.  C,  1911. 

Sudworth,  George  B.,  and  Mell,  Clayton  D.:  Identification  of  North 
American  Walnut  Woods.  Hardwood  Record,  Chicago,  Sept.  10  and  25, 
1914. 

Thelen,  Rolf:  The  Structural  Timbers  of  the  Pacific  Coast.  Proc.  Am. 
Soc.  Test  Mat.,  8:  558-567,  1908. 

Zon,  Raphael:  Balsam  Fir.  Bui.  No.  55,  U.  S.  Dept.  Agr.,  Washington, 
D.  C,  1914. 

2.    Uses  of  Woods;  Wood-using  Industries 

Armstrong,  Andrew  K.:  Wood-using  Industries  of  California.  Bui.  No. 
3,  Cal.  State  Board  of  Forestry,  Sacramento,  1912. 

Betts,  H.  S.:  Properties  and  Uses  of  the  Southern  Pines.  Cir.  164,  U.  S. 
Forest  Service,  Washington,  D.  C.,*1909. 


ECONOMIC    WOODS    OF   THE   UNITED   STATES  123 

Brooks,  A.  B.:  Wood  Manufacturing  Industries  of  West  Virginia.  Vol.  5, 
Chap.  9,  pp.'_430-461,  West  Virginia  Geological  Survey,  Morgantown,  W.  Va., 
1910. 

Brush,  W.  D.:  Utilization  of  Elm.  Bui.  No.  683,  U.  S.  Dept.  Agr.,  Wash- 
ington, D.  C,  1918. 

Cline,  McGarvey,  and  Knapp,  J.  B.:  Properties  and  Uses  of  Douglas  Fir. 
Bui.  38,  U.  S.  Forest  Service,  Washington,  D.  C,  1911. 

Dodge,  Charles  Richards:  A  Descriptive  Catalogue  of  Manufactures 
from  Native  Woods,  as  Shown  in  the  Exhibit  of  the  U.  S.  Dept.  of  Agr.  at  the 
World's  Industrial  and  Cotton  Exposition  at  New  Orleans,  La.  Special  Re- 
port No.  10,  U.  S.  Dept.  Agr.,  Washington,  D.  C,  1886. 

Dunning,  C.  W. :  The  Wood-using  Industries  of  Idaho.  Reprint,  Pacific 
Lumber  Trade  Journal,  Seattle,  Wash.,  July  1912. 

Dunning,  C.  W.:  Wood-using  Industries  of  Ohio.  Pub.  by  Ohio  Agr. 
Exp.  Sta.,  Wooster,  O.,  1912. 

Gould,  C.  W.,  and  Maxwell,  Hu:  The  Wood-using  Industries  of  Missis- 
sippi. Reprint,  Lumber  Trade  Journal,  New  Orleans,  La.,  March  15,  1912, 
pp.  19-29. 

Gould,  Clark  W.,  and  Maxwell,  Hu:  The  Wood-using  Industries  of 
Tennessee.  Reprint,  The  Southern  Lumberman,  Nashville,  Tenn.,  May  25, 
1912. 

Hall,  William  L.,  and  Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the 
United  States:  I.  Cedars,  Cypresses,  and  Sequoias.  Bui.  95,  U.  S.  Forest 
Service,  Washington,  D.  C.,  1911. 

Hall,  William  L.,  and  Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the 
United  States:  II.  Pines.  Bui.  99,  U.  S.  Forest  Service,  Washington,  D.  C, 
1911. 

Harris,  John  T.,  and  Maxwell,  Hu:  The  Wood-using  Industries  of 
Alabama.     Reprint  Lumber  Trade  Journal,  New  Orleans,  La.,  May  1,  1912. 

Harris,  J.  T.,  Maxwell,  Hu,  and  Kiefer,  Francis:  Wood-using  In- 
dustries and  National  Forests  of  Arkansas.  Bui.  106,  U.  S.  Forest  Service, 
Washington,  D.  C,  1912. 

Harris,  John  T.:  Wood-using  Industries  of  New  York.  Series  14,  No.  2, 
N.  Y.  State  College  of  Forestry,  Syracuse,  N.  Y.,  1913. 

Hatch,  Charles  F.:  Manufacture  and  Utilization  of  Hickory,  1911.  Cir. 
187,  U.  S.  Forest  Service,  Washington,  D.  C,  1911. 

Hatch,  Charles  F.,  and  Maxwell,  Hu:  The  Wood-using  Industries  of 
Missouri.  Reprint,  St.  Louis  Lumberman,  St.  Louis,  Mo.,  March  15,  1912,, 
pp.  68-82. 

Hoffman,  B.  E. :  Alaska  Woods,  Their  Present  and  Prospective  Uses.  For. 
Quarterly,  11:  2:  185-200,  June  1913. 

Kellogg,  R.  S.:  Lumber  and  Its  Uses.  Chicago,  Radford  Architectural 
Co.,  1914. 

Knapp,  Joseph  Burke:  Montana's  Secondary  Wood-using  Industries. 
Reprint,  The  Timberman,  Portland,  Ore.,  Nov.  1912. 

Lamb,  G.  N.:  Farm  Woodlot  Timber:  Its  Uses  and  Principal  Markets. 
Bui.  No.  51,  Dept.  of  Agr.  Extension,  Purdue  University,  LaFayette,  Ind.,  1916. 


124  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

Lamb,  George  N.:  Willows:  Their  Growth,  Use,  and  Importance.  Bui. 
No.  316,  U.  S.  Forest  Service,  Washington,  D.  C.,  1915. 

Lazenby,  William  R. :  The  Economic  Uses  of  Wood.  Pub.  by  Ohio  State 
University,  Columbus,  O.,  1904. 

Lazenby,  William  R. :  Qualities  and  Uses  of  the  Woods  of  Ohio.  Vol.  20, 
No.  9,  Ohio  State  University.     Bui.  6,  Vol.  2,  No.  2,  Ohio  Biol.  Survey,  1916. 

Lee,  H.  N.:  Canadian  Woods  for  Structural  Timbers.  Bui.  No.  59, 
Forestry  Branch,  Dept.  Int.  Canada,  Ottawa,  1917. 

Lewis,  R.  G.,  and  Boyce,  W.  Guy  H.:  Wood-using  Industries  of  the 
Maritime  Provinces.  Bui.  No.  44,  Forestry  Branch,  Dept.  of  Int.  Canada, 
Ottawa,  1914. 

Lewis,  R.  G.,  and  Boyce,  W.  Guy  H.:  Wood-using  Industries  of  Ontario. 
Bui.  No.  36,  Forestry  Branch,  Dept.  Int.  Canada,  Ottawa,  1913. 

Lewis,  R.  G.,  and  Boyce,  W.  Guy  H.:  Wood-using  Industries  of  the 
Prairie  Provinces.  Bui.  No.  50,  Forestry  Branch,  Dept.  Int.  Canada,  Ottawa, 
1915. 

Lewis,  R.  G.,  and  Doucet,  J.  A.:  Wood-using  Industries  of  Quebec.  Bui. 
No.  63,  Forestry  Branch,  Dept.  Int.  Canada,  Ottawa,  1918. 

MacMillan,  H.  R.:  Wood-using  Industries,  1910.  Bui.  No.  24,  Forestry 
Branch,  Dept.  Int.  Canada,  Ottawa,  1912. 

Mason,  D.  T.:  Utilization  and  Management  of  Lodgepole  Pine  in  the 
Rocky  Mountains.  Bui.  No.  234,  U.  S.  Forest  Service,  Washington,  D.  C, 
1915. 

Maxwell,  Hu:  Uses  of  Commercial  Woods  of  the  United  States:  Beech, 
Birches,  and  Maples.  Bui.  No.  12,  U.  S.  Forest  Service,  Washington,  D.  C, 
1913. 

Maxwell,  Hu:  The  Uses  of  Wood.  American  Forestry,  24:293-300, 
May  to  Dec.  1918. 

Maxwell,  Hu:  Utilization  of  Osage  Orange.  Pub.  by  Farm  Wagon  Dept., 
Natl  Implement  and  Vehicle  Ass'n.,  U.  S.  A.,  1911. 

Maxwell,  Hu:  Wood-using  Industries  of  Florida.  Pub.  by  Fla.  Dept.  of 
Agr.,  Talahassee,  1912. 

Maxwell,  Hu  :  The  Wood-using  Industries  of  Louisiana.  Reprint,  Lumber 
Trade  Journal,  New  Orleans,  La.,  Jan.  1,  1912. 

Maxwell,  Hu:  The  Wood-using  Industries  of  Maryland.  Bui.  Maryland 
State  Board  of  Forestry,  Baltimore,  Md.,  1910. 

Maxwell,  Hu:  A  Study  of  the  Massachusetts  Wood-using  Industries. 
Pub.  by  State  of  Mass.,  Boston,  1910. 

Maxwell,  Hu:  Wood-using  Industries  of  Michigan.  Pub.  by  Public 
Domain  Commission,  Lansing,  Mich.,  1912. 

Maxwell,  Hu,  and  Harris,  John  T. :  The  Wood-using  Industries  of  Iowa. 
Pub.  by  Agr.  Exp.  Sta.,  Iowa  State  College  of  Agr.  and  Mechanic  Arts,  Ames, 
Iowa,  1913. 

Maxwell,  Hu,  and  Harris,  John  T. :  Wood-using  Industries  of  Vermont. 
Forestry  Pub.  No.  11,  Dept.  of  Agr.  and  Forestry  of  the  State  of  Vt.,  Rutland, 
Vt.,  1913. 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  125 

Maxwell,  Hu,  and  Harris,  John  T. :  Wood-using  Industries  of  Minnesota. 
Pub.  by  Minn.  State  Forestry  Board,  St.  Paul,  Minn.,  1913. 

Maxwell,  Hu,  and  Hatch,  Charles  F. :  The  Wood-using  Industries  of 
Texas.     Reprint,  Lumber  Trade  Journal,  New  Orleans,  La.,  June  15,  1912. 

Nellis,  J.  C. :  The  Wood-using  Industries  of  Indiana.  Reprint,  Hardwood 
Record,  Chicago,  111.,  March  1,  1916. 

Nellis,  J.  C:  The  Wood-using  Industries  of  Maine.  Report  Forest  Com- 
missioner, Waterville,  Me.,  1912. 

Nellis,  J.  C. :  Lumber  Used  in  the  Manufacture  of  Wooden  Products.  Bui. 
No.  605,  U.  S.  Dept.  Agr.,  Washington,  D.  C,  1918. 

Nellis,  J.  C,  and  Harris,  J.  T.:  Wood-using  Industries  of  West  Virginia. 
Bui.  No.  10,  W.  Va.  Dept.  of  Agr.,  Charleston,  W.  Va.,  1915. 

Oakleaf,  Howard  B.:  Wood-using  Industries  of  Oregon,  with  Special  Re- 
ference to  the  Properties  and  Uses  of  Oregon  Woods.  Pub.  by  Ore.  Conserva- 
tion Ass'n.,  Portland,  Ore.,  1911. 

Oakleaf,  Howard  B.:  Washington's  Secondary  Wood-using  Industries. 
Pacific  Lumber  Trade  Journal,  Seattle,  Wash.,  1911. 

Pierson,  Albert  H.:  Wood-using  Industries  of  Connecticut.  For.  Pub. 
No.  7,  Bui.  174,  Conn.  Agr.  Exp.  Sta.,  New  Haven,  Conn.,  Jan.  1913. 

Pierson,  Albert  H.:  Wood-using  Industries  of  New  Jersey.  Pub.  by 
Forest  Park  Reservation  Com.  of  New  Jersey,  Union  Hill,  N.  J.,  1914. 

Pratt,  Merritt  B.:  The  Use  of  Lumber  on  California  Farms.  Bui.  No. 
299,  Agr.  Exp.  Sta.,  Berkeley,  Cal.,  1918. 

Simmons,  Roger  E.:  The  Wood-using  Industries  of  Illinois.  Pub.  by  Uni- 
versity of  Illinois,  Urbana,  111.,  1911. 

Simmons,  Roger  E.:  A  Study  of  the  Wood-using  Industries  of  Kentucky. 
Pub.  by  Dept.  Agri.,  Labor  and  Statistics,  Frankfort,  Ky.,  1910. 

Simmons,  Roger  E.:  Wood-using  Industries  of  New  Hampshire.  Pub. 
by  State  of  N.  H.  Forestry  Com.,  Concord,  N.  H.,  1912. 

Simmons,  Roger  E.:  Wood-using  Industries  of  North  Carolina.  Econ. 
Paper  No.  XX,  N.  C.  Econ.  and  Geol.  Survey,  Raleigh,  N.  C,  1910. 

Simmons,  Roger  E. :  Wood-using  Industries  of  Pennsylvania.  Bui.  No.  9, 
Dept.  of  Forestry,  Harrisburg,  Pa.,  April,  1914. 

Simmons,  Roger  E.:  Wood-using  Industries  of  Virginia.  Pub.  by  Dept. 
of  Agr.  and  Immigration,  Richmond,  Va.,  1912. 

Smith,  Franklin  H. :  A  Study  of  the  Wisconsin  Wood-using  Industries. 
Pub.  by  Forestry  Dept.,  Madison,  Wis.,  1910. 

Surface,  G.  T.:  The  Commercial  Woods  of  the  United  States  and  Their 
Uses.     Reprint,  Bui.  Geog.  Soc.  of  Phila.,  Vol.  VIII,  No.  3,  July  1910. 

Swan,  O.  T.:  The  Wood-using  Industries  of  Georgia.  Reprint,  Lumber 
Trade  Journal,  New  Orleans,  La.,  Mar.  15,  1915. 

Wolfe,  Stanley  L.:  Wood-using  Industries,  of  South  Carolina.  Pub.  by 
Dept.  of  Agr.,  Commerce  and  Industries,  Columbia,  S.  C.,  1913. 


APPENDIX 

The  Woods  of  the  United  States 

Wood  of  economic  importance  is  obtained  from  certain  repre- 
sentatives of  the  highest  sub-division  of  the  plant  world  —  the 
Spermatophytes  or  true  flowering  and  seed-bearing  plants.  Bot- 
anists separate  this  large  group,  chiefly  on  the  basis  of  floral  and 
fruit  characters,  into  two  classes,  viz.,  the  Gymnosperms  and  the 
Angiosperms. 

The  Gymnosperms  are  all  woody  plants,  either  trees  or  shrubs. 
Of  the  fifteen  genera  indigenous  to  the  United  States,  two  (Taxus 
and  Tumion  or  Torreya)  belong  to  the  Taxaceae  or  yew  family  and 
are  of  little  or  no  commercial  importance.  The  other  thirteen 
belong  to  the  Coniferse  or  true  cone-bearers. 

The  woods  of  the  Coniferse,  commonly  known  as  coniferous 
woods  or  softwoods,  are  esteemed  for  structural  purposes  because 
they  combine  a  high  degree  of  strength  and  stiffness  with  com- 
paratively light  weight  and  ease  of  manipulation.  They  are 
separable  into  (a)  the  pine-like  and  (b)  the  cedar-like.  The  first 
includes  the  pines  (Pinus),  Douglas  fir  (Pseudotsuga) ,  spruces 
(Picea),  larches  (Larix),  true  firs  (Abies),  and  the  hemlocks  (Tsuga). 
The  second  group  embraces  the  junipers  (Juniperus),  various 
cedars  (Chamcecy parts,  Thuya,  Libocedrus) ,  the  cypresses  (Cupres- 
sus  and  Taxodium),  and  the  sequoias  (Sequoia).  The  cedar-like 
woods  are  characterized  by  their  resistance  to  decay  and  also,  with 
the  exception  of  Taxodium  and  Sequoia,  by  their  fragrant  scent. 

The  Angiosperms  are  very  abundantly  represented  in  the  flora 
of  this  country  and  include  a  large  proportion  of  herbaceous  forms. 
Two  sub-classes  are  recognized,  viz.,  the  Monocotyledons  and  the 
Dicotyledons,  referring  to  the  number  of  cotyledons  or  seed-leaves 
of  the  embryo.  There  are  also  fundamental  differences  in  their 
stem  structures. 

Monocotyledonous  stems  are  mostly  unbranched  and  the  wood 
is  confined  to  isolated  strands  disposed  irregularly  in  a  mass  of 
softer  tissue,  becoming  more  and  more  compact  toward  the  surface. 
In  general,  there  are  lacking  certain  important  features  which 
characterize  the  stems  of  both  Gymnosperms  and  Dicotyledons, 

127 


128  ECONOMIC   WOODS   OF   THE    UNITED   STATES 

viz.,  (a)  a  distinct  central  core  of  pith,  (b)  a  covering  of  bark,  and 
between  these  two  (c)  a  fairly  uniform  mass  of  wood  which  in- 
creases in  thickness  by  the  addition  of  periodic  layers  on  the  outside. 

Some  well-known  representatives  of  the  Monocotyledons  are 
the  grasses  (including  maize,  wheat,  many  other  cereals,  the  bam- 
boos, etc.),  the  sedges,  lilies,  bananas,  rattans,  palms,  and  yuccas. 
The  woody  types  are  confined  chiefly  to  tropical  and  sub-tropical 
regions  where  they  are  extensively  used  but  not  in  the  form  of 
lumber.  There  are  seven  kinds  of  palms  and  nine  kinds  of  yuccas 
of  tree  size  native  to  the  United  States.  They  are  used  to  some 
extent  locally  but  as  a  commercial  source  of  wood  are  wholly 
negligible. 

As  stated  on  p.  7  there  are,  according  to  Sargent's  "  Manual  of 
the  Trees  of  North  America,"  62  families  and  162  genera  of  Dico- 
tyledons with  representatives  of  tree  size  in  this  country.  The 
total  number  of  species  described  is  618.  Various  others  have 
been  introduced,  mostly  for  decorative  purposes  but  also  to  a  small 
extent  for  forest  planting,  and  a  few  have  become  naturalized,  but 
only  in  rare  instances  do  their  woods  contribute  to  our  commercial 
supply.  Sud worth's  "  Check  List "  *  enumerates  495  trees,  includ- 
ing a  few  which  have  become  thoroughly  naturalized.  This  dis- 
crepancy is  accounted  for  mostly  by  the  large  number  of  species  of 
Crataegus,  153  in  all,  described  by  Sargent  as  against  25  listed  by 
Sudworth.  Not  a  single  representative  of  this  genus  is  of  commer- 
cial importance  for  its  wood,  and  of  the  45  species  belonging  to 
the  other  genera  of  the  Rosacese  only  one,  Prunus  serotina,  is  a 
source  of  valuable  lumber.  One  willow  out  of  24  species,  about  22 
oaks  out  of  a  total  of  54,  and  about  a  dozen  pines  out  of  the  28 
native  to  this  country  are  commercially  valuable.  In  the  Govern- 
ment reports  on  lumber  production  only  30  kinds  are  considered 
of  sufficient  importance  to  justify  separate  tabulation,  while  about 
20  are  grouped  under  the  single  heading  of  "minor  species." 

The  following  list  includes  the  most  important  families  and 
genera  of  the  Dicotyledons.  Included  in  it  are  seven  families 
which  are  really  of  secondary  importance  so  far  as  the  amount  of 
the  wood  produced  is  concerned.  These  are,  Aquifoliacese, 
Bignoniacese,  Ebenaceae,  Hippocastanacese,  Lauracess,  Meliacese, 
and  Moracese.  (Cornacese  includes  Nyssacese  of  Sargent.) 

*  Sudworth,  George  B.:  Check  last  of  the  Forest  Trees  of  the  United 
States,  Their  Names  and  Ranges.  Bui.  No.  17,  U.  S.  Division  of  Forestry, 
Washington,  D.  C,  1898. 


ECONOMIC   WOODS   OF   THE    UNITED   STATES 


129 


TABLE   V 

Important  Families  and  Genera  of  Dicotyledons  in  the 

United  States 


Aceraceoe 

Acer  (maple) 
Aquifoliacece 

Ilex  (holly) 
Betulacece 

Alnus  (alder) 

Betula  (birch) 
Bignoniacece 

Catalpa  (catalpa) 
Cornacece 

Cornus  (dogwood) 

Nyssa  (tupelo) 
Ebenacece 

Diospyros  (persimmon; 
Fagacece 

Castanea  (chestnut) 

Castanopsis  (chinquapin) 

Fagus  (beech) 

Quercus  (oak) 
Hamamelidacece 

Liquidamabar  (red  gum) 
Hippo castanacecB 

iEsculus  (buckeye) 
J  uglandacecB 

Hicoria  (hickory) 

Juglans  (walnut) 
Lauracece 

Sassafras  (sassafras) 


Leguminosce 

Gleditsia  (honey  locust) 

Gymnocladus  (Ky.  coffee-tree) 

Robinia  (black  locust) 

Prosopis  (mesquite) 
Magnoliacece 

Liriodendron  (tulip-tree) 

Magnolia  (magnolia;  cucumber) 
Meliacece 

Swietenia  (mahogany) 
Moraceoe 

Morus  (mulberry) 

Toxylon  (Osage  orange) 
Oleaceaz 

Fraxinus  (ash) 
Platanacece 

Platanus  (sycamore) 
Rosacea? 

Prunus  (black  cherry) 
Salicacece 

Populus  (poplar;  cottonwood) 

Salix  (willow) 
Tiliaceos 

Tilia  (basswood) 
Ulmacece 

Celtis  (hackberry) 

Ulmus  (elm) 


TABLE  VI 
Numerical  Conspectus  of  the  Trees  of  the  United  States 


Class 

Number  of 
Families 

Number  of 
Genera 

Number  of 
Species 

Number  of 

Economic 

Species 

which 

can  be  iden- 

Total 

Economic 

Total 

Economic 

Total 

Economic 

tified  from 

the  Wood 

alone 

Gymnosperms 

2 

1 

15 

12 

84 

37 

25-30 

CO 

2 

Monocotyledons 

2 

0 

8 

0 

21 

0 

CO 

O 

"So 

a 
< 

Dicotyledons 

62 

22 

162 

40 

618 

100 

55-65 

Totals 

66 

23 

185 

52 

723 

137 

80-95 

130  ECONOMIC   WOODS   OF   THE   UNITED   STATES 


WOOD    STRUCTURE 

Wood  is  a  fibrous  structure  composed  of  cells  which  are  for  the 
most  part  greatly  elongated  in  a  vertical  or  axial  direction.  Longi- 
tudinal surfaces  accordingly  show  the  fibrous  nature  of  wood  to  the 
best  advantage,  while  the  cross  section  appears  under  the  micro- 
scope more  or  less  like  a  fine  honey-comb.  Some  wood  cells  are 
large  enough  to  be  readily  seen,  others  are  at  the  limit  of  vision 
and  require  a  hand  lens  for  distinctness,  and  a  much  larger  number 
are  not  individually  visible  without  considerable  magnification. 

All  wood  cells  when  first  formed  contain  living  protoplasm  but 
a  large  proportion  of  them  apparently  lose  it  very  early.  Such 
cells  provide  channels  for  sap-flow  from  root  to  leaf,  lend  strength 
and  rigidity  to  the  stem,  and  in  some  instances  supply  spaces  for 
storage  of  excess  food  and  reservoirs  for  waste  products.  Since 
these  functions  are  in  part  physiological  it  seems  unlikely  that  the 
protoplasm  has  entirely  disappeared  from  the  elements  concerned, 
even  if  its  presence  cannot  be  directly  demonstrated,  since  cells 
without  living  protoplasm  can  only  function  mechanically. 

The  wood  cells  which  obviously  retain  living  protoplasm 
throughout  their  functional  period  may  be  referred  to  as  food  cells 
(parenchyma)  since  they  are  primarily  concerned  with  the  dis- 
tribution and  storage  of  plant  food.  This  food  is  elaborated  in 
the  leaves  (and  other  green  tissues)  and  is  transported  along  the 
stem  chiefly  through  certain  channels  (sieve-tubes  of  the  phloem) 
in  the  inner  bark.  The  cells  (ray  parenchyma)  which  divert  por- 
tions of  the  food  current  into  the  wood  are  typically  elongated  in  a 
horizontal  or  radial  direction,  while  those  (wood  parenchyma) 
which  distribute  it  vertically  in  the  stem  are  axially  elongated. 
Plant  food  assumes  various  forms,  the  principal  ones  being  starch, 
sugars  and  fats;  the  change  from  one  form  to  another  is  brought 
about  by  the  action  of  certain  ferments  or  enzymes. 

Structurally,  a  wood  cell  consists  of  a  cell  wall  of  ligno-cellulose, 
inclosing  a  lumen  or  cavity  (with  or  without  visible  contents),  and 
completely  surrounded  by  a  pectic  layer  called  the  middle  lamella. 
The  lignified  wall  provides  a  strong  and  rigid  framework.  The 
middle  lamella  limits  the  individual  cells  and  cements  them  firmly 
together  to  form  the  wood-mass.  The  cavity  serves  various  pur- 
poses such  as  the  transportation  of  food  and  water,  aeration, 
storage,  etc.,  and  must  accordingly  be  in  communication  with  the 


ECONOMIC   WOODS   OF   THE   UNITED   STATES  131 

cavities  of  adjacent  cells  and  in  some  instances  with  intercellular 
spaces  also. 

Where  the  cell  walls  are  thin  enough  there  is  no  need  for  special 
provision  for  intercommunication.  The  process  of  thickening 
reduces  the  permeability  of  the  walls  and  makes  necessary  the 
leaving  of  thin  or  unthickened  spots  called  pits.  Were  the  wall 
uniformly  thickened  throughout,  the  lumen  would  become  isolated 
and  the  function  of  the  cell  would  be  reduced  to  that  of  reinforce- 
ment only,  a  condition  approximated  in  the  libriform  fibres  of 
certain  woods  such  as  Toxylon  and  Robinia.  At  the  other  ex- 
treme, there  are  elements  (vessels)  concerned  with  the  rapid  con- 
duction of  water  which  are  composed  of  vertical  series  of  cells 
whose  pits  at  the  ends  have  given  place  to  true  openings  or  per- 
forations. The  only  fundamental  difference  between  a  perforation 
and  a  pit  is  that  in  a  pit  the  middle  lamella,  somewhat  modified, 
forms  a  limiting  or  pit  membrane.  The  presence  of  minute  per- 
forations in  this  membrane  can  be  demonstrated  by  passing  finely 
divided  solid  particles  through  it. 

Some  cells  have  simple  pits  while  others  appear  under  the 
compound  microscope  to  have  a  more  or  less  distinct  border. 
This  border  is  due  to  the  wall  overhanging  the  margin  of  the  pit 
membrane.  Pits  between  food-cells  are  simple  while  those  be- 
tween water-carriers  are  bordered.  Where  the  two  types  of  cells 
are  in  communication  the  half  of  the  pit  in  the  food-cell  is  always 
simple  and  the  corresponding  portion  in  the  other  may  be  either 
simple  or  bordered.  In  the  latter  case  the  pit  is  structurally  half- 
bordered,  though  in  surface  view  it  may  not  be  distinguishable 
from  one  that  is  bordered  on  both  sides.  Pits  exhibit  a  wide  range 
of  variation  in  size,  shape  and  arrangement,  and  possess  high  value 
for  purposes  of  classification  of  woods.  (For  further  details  see 
pp.  31-35.) 

CLASSIFICATION   OF   THE    ELEMENTS   OF   SECONDARY   WOOD 

On  p.  13  the  cellular  elements  of  wood  are  referred  to  three 
principal  types,  viz.,  vascular,  fibrous  and  parenchymatous. 
Some  authors  prefer  the  following  classification:  (a)  vessels  (cell- 
fusions  serving  for  the  conduction  of  water) ;  (6)  parenchyma  (food 
cells  which  conduct  and  store  carbohydrates);  (c)  prosenchyma 
(cells  serving  chiefly  to  give  mechanical  support  but  often  partici- 
pating in  functions  of  the  other  groups).     The  prosenchyma  in- 


132  ECONOMIC   WOODS   OF   THE   UNITED    STATES 

eludes  all  of  the  vertical  elements  of  the  wood  except  vessels  and 
parenchyma,  namely,  libriform  fibres,  septate  fibres,  intermediate 
or  substitute  fibres,  fibre-tracheids,  and  tracheids. 

Libriform  fibres  are  the  cells  referred  to  on  p.  18  as  typical  wood 
fibres.  Fibre-tracheids  are  fibrous  cells  with  distinctly  bordered 
pits  and  are  intermediate  between  libriform  fibres  and  vessel-like 
tracheids;  they  do  not  occur  in  Gymnosperms  though  the  tracheids 
of  the  late  wood  might  with  some  justification  be  so-called. 

The  following  diagram  shows  the  relationships  of  the  various 
elements.  In  this  the  tracheid  appears  as  the  dominant  element. 
Vessels  are  composed  of  segments  which  were  originally  tracheids 
before  fusion;  intermediate  forms  occur.  Fibre-tracheids  and 
libriform  fibres  may  be  considered  as  modifications  of  the  tracheid 
in  which  the  mechanical  function  of  strength  is  emphasized  at  the 
expense  of  water  conduction.  Intermediate  forms  between  these 
cells  and  parenchyma  are  shown  in  the  diagram  which  were  not 
brought  out  in  the  other  classifications.  Epithelial  cells  of  resin 
ducts  are  shown  as  specialized  forms  of  parenchyma. 


TRACHEIDS- 

Fibre-tyuheids 

t— 

Ray  tracheids 

_     '  Substitute  fibres  ' 
"  I  Septate  fibres       , 

Ray  parenchyma 

1         \ 

1               ^>EP 

Wood'parenchyma 

thelial  cells 

Librifo 

m  fibres 

VESSELS 

Vessels  are  compound  elements;  they  are  composed  of  segments 
which  have  become  fused  at  the  ends  (and  sometimes  at  the  sides 
as  well)  into  vertical  series.  Each  segment  normally  arises  from  a 
single  cambial  cell  and  when  first  formed  is  completely  inclosed  by 
the  middle  lamella  and  is  morphologically  a  tracheid.  After  fusion 
the  cells  function,  not  as  a  series  of  individuals,  but  as  a  continuous 
tube. 

The  segments  may  abut  on  each  other  squarely  at  the  ends 
or  overlap  more  or  less.  Both  forms  may  occur  in  the  same  vessel, 
though  decidedly  elongated  tips  are  characteristic  of  certain 
species.  Such  tips  are  usually  provided  with  bordered  pits  and  in 
some  instances  exhibit  spiral  thickenings  even  though  the  body  of 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  133 

the  segment  does  not.  Sometimes  segments  are  fused  through 
their  lateral  walls,  or  the  end  of  one  segment  may  be  joined  to  the 
lateral  wall  of  another,  but  such  forms  are  to  be  considered  ex- 
ceptional. 

The  plane  of  contact  between  segments  may  be :  (a)  horizontal 
or  transverse,  that  is,  at  right  angles  to  the  axis  of  the  vessel;  (6) 
oblique  or  inclined,  almost  always  facing  the  ray;  (c)  vertical  or 
longitudinal.  The  last  may  be  considered  an  extreme  form  of  the 
oblique  unless  it  occurs  where  segments  are  fused  through  their 
lateral  walls. 

VESSEL   PERFORATIONS 

The  opening  from  one  segment  into  another  is  called  the  vessel 
perforation.  The  various  types  and  modifications  of  vessel  per- 
forations supply  features  highly  important  for  diagnostic  purposes. 
The  two  principal  forms  are  :  (a)  the  simple  and  (6)  the  scalariform. 
Insofar  as  our  commercial  woods  are  concerned  knowledge  of  these 
two  types  is  sufficient.  There  are  various  other  forms,  however, 
though  most  of  them  are  modifications  or  malformations  of  the 
two  principal  types.  The  reticulate  form  is  not  uncommon, 
especially  in  the  Rosacea?,  and  tendency  to  it  is  seen  in  the  branch- 
ing and  anastomosing  bars  in  almost  all  woods  with  scalariform 
perforations.  In  Rosa  sp.  the  author  has  observed  in  a  single 
section,  simple  (predominating),  scalariform,  reticulate,  pit- 
perforate,  and  various  composite  perforations. 

The  following  classification  shows  the  range  of  variation  in 
perforations,  though  there  are  innumerable  forms  of  the  composite. 
A  few  instances,  mostly  exotics,  are  cited  as  illustrations  of  the 
rarer  kinds. 

TYPES    OF   VESSEL   PERFORATIONS 

Simple:  (Single  opening,  circular,  elliptical  or  elongated-elliptical.) 
Scalariform:    (Openings    slit-like   or   elongated   between    cross 
bars.) 
Bars  transverse  (Common  form). 

Bars  vertical  (Very  rare.     In  certain  Composite  and  Axyris 
amarantoides) . 
Reticulate:  (Irregular  openings  as  meshes  between  anastomosing 
bars.) 


134  ECONOMIC   WOODS    OF   THE   UNITED   STATES 

Multiperforate  :  (Plural  circular  or  elliptical  openings.) 

Few  comparatively  large  openings  (Ephedra;  occasionally  in 

Vaccinium  uliginosum  and  Leitneria  floridana) . 
Numerous  small  openings  (Canella  alba;  Menziesia  ferruginea) . 
Pit-perforate:   (Not  readily  distinguishable  from  pits.)    (Oc- 
casionally in  Meisteria  cernua,   Lithospermum  fruiticosum, 
Cheirodendron  sp.,  Rosa  sp.) 
Composite:  (Mostly  malformations  occasionally  met  with.) 
Simple-scalariform :  (Quillaja,  certain  Bignoniacese,  etc.) 
Simple-reticulate:   (Sorbus  aucuparia,  Sidonia  vulgaris,   Rosa 

sp.,  Cheirodendron  gaudichaudii,  etc.) 
Scalariform-reticulate :  (Didymopanax  morototoni.) 

Simple  perforations  characterize  a  large  majority  of  our  native 
woods.  Where  the  plane  of  perforation  is  transverse  or  only 
slightly  inclined  the  simple  type  is  almost  invariably  found. 
Where  the  perforation  is  inclined  it  may  be  either  simple  or  scalari- 
form.  The  opening  may  be  circular,  elliptical,  or  oblong- 
elliptical.  The  elliptical  form  prevails  where  the  plane  of  perfora- 
tion is  oblique.  Usually  the  end  walls  are  not  completely  removed 
in  the  formation  of  a  simple  perforation  and  the  border  remaining 
is  called  the  annular  ridge.  This  ridge  may  vary  in  width  from 
very  narrow  to  fairly  broad. 

There  are  a  number  of  families  in  which  all  of  the  investigated 
genera  have  exclusively  simple  perforations.  Prominent  among 
these  are  the  following:  Aceracese,  Bignoniacese,  Ebenacese,  Jug- 
landacese,  Leguminosse,  Moracese,  Salicaceae,  and  Tiliacese.  There 
are  a  number  of  others  in  which  the  simple  type  predominates  but 
where  scalariform  perforations  are  occasionally  or  rarely  found  in 
the  secondary  wood  or  where,  from  the  nature  of  the  perforations 
in  the  primary  wood,  they  are  to  be  expected.  Important  ex- 
amples are  the  Betulacese,  Fagacese  and  Rosacea?.  Both  simple 
and  scalariform  perforations  may  occur  commonly  side  by  side  in 
the  secondary  wood,  as  for  example,  in  Fagus  and  Platanus.  Oc- 
casionally a  segment  is  found  in  which  the  perforation  at  one  end 
is  simple  and  at  the  other  scalariform.  Table  VII  includes  nearly 
all  of  the  genera  of  native  trees  having  vessel  perforations  exclu- 
sively or  predominately  simple.  The  representatives  of  the 
families  marked  with  (*)  exhibit  some  tendency  toward  the  forma- 
tion of  the  scalariform  type.  The  more  important  genera  are 
shown  in  italics. 


ECONOMIC   WOODS    OF   THE    UNITED   STATES 


135 


TABLE  VII 

Indigenous  Woods  with  Vessel  Perforations  Exclusively  or  Pre- 

dominantly  Simple 

ACERACE^E 

Ericaceae  * 

Parkinsonia 

Malus 

Acer 

Arbutus 

Prosopis 

Prunus 

ANACARDIACEiE 

Arctostaphylos 

Robinia 

Sorbus 

Cotinus 

EUPHORBIACE.E  * 

Sophora 

Vauquelinia 

Rhus 

Drypetes 

Zygia 

Rubiace^e 

AnONACEjE 

FaGACEjE  * 

Leitneriace^e 

Pinckneya 

Anona 

Castanea 

Leitneria 

RUTACE.E 

Asimina 

Castanopsis 

MAGNOLIACE.E  * 

Amyris 

Betulace^e  * 

Fagus 

Magnolia 

Fagara 

Carpinus 

Quercus 

acuminata 

Helietta 

Ostrya 

Hippocastanace^e 

Meliace^e 

Ptelea 

Bignoniaceje 

/Esculus 

Sivietenia 

Salicace^e 

[    Catalpa 

Juglandace^e 

MORACE.E 

Populus 

Chilopsis 

Hicoria 

Morus 

Salix 

Crescentia 

Juglans 

Toxylon 

Sapindace^e 

Boraginace^e 

Laurace^e  * 

Oleace^e 

Exothea 

Ehretia 

Ocotea 

Chionanthus 

Hypelate 

Burserace^e 

Persea 

Fraxinus 

Sapindus 

Bursera 

Sassafras 

Osmanthus 

Ungnaria 

Cactace^e 

Umbellularia 

POLYGONACE^J 

Sapotace^e 

Cereus 

Leguminosjs 

Coccolobis 

Bumelia 

Opuntia 

Acacia 

RhAMNACEjE 

Chrysophyllum 

CaPPARIDACEjE 

Cercidium 

Ceanothus 

Sideroxylon 

Capparis 

Cercis 

Colubrina 

Simarubace^e 

Caprifoliace^e* 

Cladrastis 

Condalia 

Ailanthus  (Nat.) 

Sambucus 

Dalea 

Krugiodendron 

Simaruba 

COMBRETACEiE 

Eysenhardtia 

Reynosia 

TlLIACE^E 

Buceras 

Gleditsia 

Rosacea  * 

Tilia 

Conocarpus 

Gymnocladus 

Amelanchier 

UlMACEjE  * 

Laguncularia 

Icthyomethia 

Cercocarpus 

Celtis 

Ebenace.e 

Leucsena 

Chrysobalanus 

Planera 

Diospyros 

Lysiloma 
Olneya 

Crataegus 

Ulmus 

Heteromeles 

Zygophyllace^: 

Lyonothamnus 

Guaiacum 

*  With  some  tendency  to  scalariform,  particularly  in  the  region  of  primary  wood. 

Scalariform  perforations  look  like  a  grid-iron  or  grating  with  an 
elliptical  or  elongated-elliptical  contour.  The  bars,  with  very 
rare  exceptions,  are  arranged  horizontally  or  transversely.  As 
the  plane  is  almost  invariably  strongly  oblique  and  facing  the  ray, 
the  structure  is  seen  to  much  better  advantage  in  radial  sections 
than  in  the  transverse  and  tangential.  Macerated  material  is 
better  still  since  a  portion  of  the  tilted  plate  is  likely  to  be  cut  off 
in  sectioning.  Bars  may  also  be  seen  in  the  lumina  of  some  of  the 
vessels  in  the  transverse  section,  especially  if  the  section  is  rather 
thick. 

The  number  of  bars  in  a  perforation  varies  from  very  few  to 


136 


ECONOMIC   WOODS   OF   THE    UNITED   STATES 


more  than  100.  Within  the  same  species,  however,  the  variation 
is  within  narrower  limits,  though  the  number  is  never  constant. 
In  Magnolia  and  Liriodendron,  for  example,  the  number  of  bars  is 
usually  less  than  15  and  the  spaces  are  wide,  while  in  Ilex,  Nyssa, 
and  Liquidambar  the  bars  are  much  more  numerous  and  are  closely 
spaced. 

In  the  following  table  are  listed  the  genera  of  native  woods  in 
which  the  vessel  perforations  are  exclusively  scalariform.  In  a 
few  cases,  perhaps,  simple  perforations  will  occasionally  be  found 
in  association  with  the  predominant  type.  The  list  is  believed  to 
be  complete  so  far  as  the  trees  are  concerned  but  not  for  the  shrubs. 
Eight  of  the  genera  yield  wood  of  commercial  importance.  It  will 
be  noted  that  no  ring-porous  wood  is  included.  Scalariform  per- 
forations are  never  found  in  large  vessels,  such  for  instance  as  are 
individually  distinct  to  the  unaided  eye,  presumably  because  the 
presence  of  gratings  would  interfere  with  the  function  of  large 
vessels,  namely,  the  rapid  conduction  of  water  in  quantity.  Solere- 
der  calls  attention  to  "the  striking  fact  that  the  occurrence  of 
scalariform  perforations  in  the  vessel  often  goes  hand  in  hand  with 
small  lumina  and  the  presence  of  bordered  pits  on  the  prosen- 
chyma."     (Systematic  Anatomy  of  the  Dicotyledons,  p.  1138.) 

TABLE  VIII 
Indigenous  Woods  with  Vessel  Perforations  Exclusively  Scalariform 


AQUDTOLIACEiE 

Ilex 
Bettjlace^e 
Betula 
Alnus 
Corylus 

CAPRIFOLIACEiE 

Viburnum 
Cornace^e 
Cornus 
Nyssa 

CyRILLACEjE 

Cyrilla_ 
Cliftonia 
Ericaceae 

Rhododendron 
Kalmia 
Vaccinium 
Andromeda 

HAMAMELIDACEiE 

Liquidambar 
Hamamelis 

*  Some  simple 


Magnoliace^e 

Liriodendron 

Magnolia  (mostly) 
Myricace.e 

Myrica* 
MyrtacejE 

Eugenia 

RhIZOPHORACEjE 

Rhizophora 
Saxifragace^e 

Philadelphus 

Hydrangea 

Ribes 
Symplocace^; 

Symplocos 
Staphyleace^e 

Staphylea 
Styrace^e 

Mohrodendron 

THEACE/E 

Gordonia 


perforations  present  in  Myrica  calijormca. 


ECONOMIC   WOODS   OF   THE    UNITED   STATES  137 


vessel  markings:  spirals  and  pits 

The  first-formed  elements  of  the  primary  wood,  those  nearest 
the  pith,  have  walls  characteristically  marked  with  annular  and 
spiral  thickenings.  During  the  process  of  rapid  elongation  of  the 
stem  these  elements  are  stretched  out,  the  spirals  or  rings  sepa- 
rated, and  the  thin,  unpitted  walls  between  the  thickenings  are 
likely  to  be  torn  and  broken  down.  Such  elements  comprise  that 
portion  of  the  primary  wood  known  as  the  protoxylem.  The  cells 
of  the  primary  wood  subsequently  formed  make  up  what  is  known 
as  the  metaxylem.  The  walls  of  the  vascular  elements  of  the 
metaxylem  are  thickened  in  a  scalariform  (ladder-like),  reticulate 
(net-like),  or  pitted  (dotted)  manner. 

The  vessels  (and  tracheids)  of  the  secondary  wood  are  pitted, 
are  without  annular  thickenings,  and  may  or  may  not  be  spiral. 
The  presence  of  spirals  is  a  valuable  diagnostic  feature,  and  the 
vessels  of  smaller  lumina  exhibit  them  to  best  advantage.  In  a 
given  wood  all  of  the  vessels  may  bear  spirals  or,  especially  where 
there  is  considerable  variation  in  the  size,  only  the  smaller  vessels 
may  be  thus  marked.  Conspicuously  large  vessels  are  invariably 
without  spirals  just  as  they  are  also  without  scalariform  perfora- 
tions. 

Spirals  exhibit  considerable  variation  in  distinctness.  In 
some  cases,  as  in  Ulmus,  they  are  very  pronounced,  in  others,  e.g., 
Tilia,  they  are  fine  but  distinct,  and  again  they  may  be  very  fine 
and  indistinct,  as  in  Magnolia.  In  some  instances,  as  previously 
stated,  only  the  overlapping  tips  of  the  segments  are  spiral  and 
these  are  often  indistinct. 

Tracheids  which  closely  resemble  vessel  segments  except  in  the 
absence  of  perforations,  have  the  same  markings  as  the  vessels. 
Fibre-tracheids  may  also  be  spiral.  This  is  normally  the  case 
in  Ilex  and  occasionally  in  certain  Rosacea?,  Ericaceae,  and  others. 
The  author  has  noted  them  in  Arbutus  and  Arctostaphylos.  Their 
presence  provides  a  valuable  diagnostic  feature. 


138 


ECONOMIC   WOODS    OF   THE    UNITED   STATES 


TABLE   IX 


Indigenous  Woods  with  Spiral  Markings  in  Part  or  in  All  of 
the  Vessels 


AcERACEiE 

Acer 

ANACARDIACEiE 

Cotinus 

Rhus 
Anonace.e 

Asimina 
Aquifoliace.e 

Ilex 
Betulacejs 

Carpinus 

Ostrya 

BlGNONIACE^E 

Catalpa 

BORAGINACE^E 

Ehretia 

CHEIRANTHODENDR.E 

Fremontodendron 
Ericaceae 
Arbutus 
Arctostaphylos 
Andromeda 
Kalmia 


Oxydendrum 
Rhododendron 
Vaccinium 
Hamamelidace^e 

Liquidambar 

HlPPOCASTANACE^E 

Msculus 
Leguminos^e 
Cercis 
Gleditsia 
Gymnocladus 
Robinia 

LEITNERIACE.E 

Leitneria 
Magnoliace^e 

Magnolia 
Meliace.e 

Melia  (Nat.) 
Morace^e 

Broussonetia  (Nat.) 

Morus 

Toxylon 
Oleace^e 

Chionanthus 

Osmanthus 


Rhamnace.e 

Ceonothus 

Rhamnus 
Rosace.e 

Amelanchier 

Aronia 

Cercocarpus 

Prunus 

Pyrus  (in  part) 

Rosa 

Sorb  us 

ScROPHULARL\CE.E 

Paulownia  (Nat.) 

SlMARUBACE.E 

Ailanthus  (Nat.) 

Koeberlinia 
Tiliace.e 

Tilia 
Ulmace.e 

Celtis 

Ulmus 

Planera 


The  vessels  of  secondary  wood  are  always  pitted.  (See  pits, 
p.  31.)  This  feature  is  seen  to  best  advantage  in  macerated 
material,  especially  where  the  vessels  are  so  large  that  most  of  the 
wall  is  cut  away  in  sectioning.  The  nature  of  the  pitting  is  de- 
termined by  the  contiguous  elements.  The  number,  form,  and 
arrangement  of  the  pits  on  a  given  area  of  wall  depends  upon  the 
particular  kind  of  cell  in  contact  there  and  the  breadth  of  the  sur- 
face of  contact.  The  character  of  the  pitting  between  adjacent 
vessels  and  between  vessels  and  ray  parenchyma  is  the  most  im- 
portant for  diagnostic  purposes. 

Pits  between  vessels  are  invariably  bordered.  The  features 
worthy  of  special  notice  are  the  arrangement  of  the  pits,  the  size 
and  contour  of  the  border,  and  the  nature  of  the  pit  mouths.  It 
is  very  common  to  find  vessels  in  groups  so  compressed  that  the 
walls  of  mutual  contact  are  flattened  out  broadly.  In  walls  thus 
flattened  it  is  not  uncommon  to  find  pits  that  are  greatly  elongated 


ECONOMIC   WOODS   OF   THE    UNITED   STATES 


139 


transversely  and  arranged  in  a  vertical  series  like  the  rungs  of  a 
ladder.  This  scalariform  pitting  is  characteristic  of  the  vessels  in 
Magnolia,  is  common  in  Liriodendron  and  Nyssa,  less  so  in  Liqui- 
dambar,  Ilex  and  Platanus,  and  of  sporadic  occurrence  in  Castanea, 
Castanopsis,  Quercus,  and  some  others.  Since  radial  grouping  is 
the  most  common,  the  pitted  surfaces  usually  appear  to  better 
advantage  in  tangential  than  in  radial  sections. 

Pits  between  vessels  and  ray  cells  are  simple  on  the  ray  side 
but  may  be  bordered,  simple,  or  transitional  on  the  other.    These 


TABLE  X 

Nature  of  Pitting  of  Vessel  Wall  where  in  Contact  with  Ray 
Parenchyma 


Family 

Bor- 
dered 

Simple 

Family 

Bor- 
dered 

Simple 

Aceraceae 

X 

x 

Anacardiaceae. 

XXX     XXX     XX 
X       x       XX       X 

Moraceae 

X > 

Anonacese 

x 

Aquifoliaceae 

x 

Araliacese 

X       > 

Nyctaginaceae 

Bignoniaceae 

X 
X 
X 

x 

Boraginaceae 

Burseraceae 

Canellaceae 

Capparidaceae 

Caprifoliaceae 

Rhizophoraceae 

Rosacea? 

X ► 

X     1 

Celastraceae 

X 
X 
X 
X 
X 

X 

X 

Cornaceae 

X    — » 

■Cyrillaceae 

1  x 

X 

Ebenaceae 

Ericaceae 

X         X 

Euphorbiaceae 

X > 

< X 

< X 

X X 

x   1   X 

xTx 

Simarubaceae 

X 

Fagaceae 

X 
X 

x 

Hamamelidaceae 

Styraceae 

Hippocastanaceae.  .  .  . 

Symplocaceae 

Juglandaceae 

X            Y 

Koeberliniaceae 

Tiliaceae 

X 
X 
X 
X 

Lauraceae 

X 

Leguminosae  f 

Verbenaceae 

Zygophyllaceae 

Magnoliaceae 

*  In  Betula  and  Alnus  the  pits  are  bordered;  in  Carpinus,  Corylus,  and  Ostrya 
simple  pits  predominate. 

t  In  Robinia  the  pits  are  predominately  simple. 


140  ECONOMIC   WOODS    OF   THE   UNITED   STATES 

pits  may  be  very  small,  medium  or  large,  often  with  considerable 
variation  in  the  same  specimen.  In  woods  with  heterogeneous 
rays  the  marginal  cells  are  usually  more  prominently  pitted  than 
the  others.  In  Gordonia  and  Oxydendrum  the  pits  are  simple 
or  only  slightly  bordered  and  are  frequently  in  scalariform  ar- 
rangement. In  Sideroxylon  and  Chrysophyllum  many  of  the  pits 
are  small  and  bordered  while  others  are  large,  simple  or  nearly  so, 
elliptical  or  elongated-elliptical  and  disposed  horizontally,  verti- 
cally or  diagonally,  resembling  perforations  rather  than  pits.  In 
Magnolia  it  is  common  to  find  much  elongated  borders  about 
groups  of  small  pits. 

Table  X  gives  for  the  different  families  the  dominant  type 
of  pits  in  vessels  where  in  contact  with  the  rays.  Where  both 
types  are  indicated  with  connecting  line  it  refers  to  their  occur- 
rence side  by  side  in  the  same  wood;  otherwise  in  different  woods 
of  same  family.  An  arrow  indicates  transitions  from  the  pre- 
vailing type. 

VESSEL    CONTENTS 

The  principal  contents  of  vessels  that  have  ceased  to  function 
actively  as  water-carriers  are  (a)  tyloses  (parenchymatous  in- 
trusions) and  (6)  various  deposits  or  excretions  such  as  gums, 
resins,  lime,  etc.  Sometimes  such  features  are  constant  and  con- 
spicuous enough  to  be  of  value  for  diagnostic  purposes.  In  a  great 
many  cases,  however,  there  is  too  much  variation  for  dependable 
results.  Generally  it  is  merely  a  question  as  to  whether  the  pores 
appear  open  or  closed  rather  than  exact  determination  by  micro- 
scopic means  of  the  presence  or  absence  of  certain  contents.  The 
feature  is  of  most  importance  in  woods  with  large  pores. 

The  following  table  gives  the  results  of  some  investigations  by 
the  author  on  the  occurrence  of  tyloses  and  gum  deposits  in  in- 
digenous woods  and  a  few  that  have  been  introduced.  The  find- 
ings do  not  in  all  cases  agree  with  those  of  other  investigators  and 
in  some  instances  are  not  to  be  considered  as  final,  especially  where 
non-occurrence  is  indicated,  owing  to  the  great  likelihood  of  varia- 
tion in  different  specimens. 


ECONOMIC   WOODS   OF   THE    UNITED   STATES 


141 


TABLE  XI 

Occurrence  of  Tyloses  and  Gum  Deposits  in  Vessels  of  Indigenous 
Woods 


Acacia 

Acer 

^Esculus 

Ailanthus  (Nat.). . . 

Alnus 

Amelanchier 

Amyris 

Anona 

Arbutus 

Arctostaphylos 

Asimina 

Avicennia 

Betula 

Broussonetia  (Nat.) 

Bumelia 

Bursera 

Carpinus 

Castanea 

Castanopsis 

Catalpa 

Celtis 

Cercidium 

Cercocarpus 

Chilopsis 

Cladrastis 

Cornus 

€otinus 

Crataegus 

Diospyros 

Eucalyptus  (Int.).  . 

Fagus 

Ficus 

Fraxinus 

Fremontodendron. . 

Gleditsia 

Guaiacum 

Gymnocladus 

Hamamelis 

Hicoria  (Carya) 

Ilex 

Juglans 

Kalmia 


Tyloses 


few 
absent 
few- 
absent 


common 
absent 


absent 

abundant 

common 

abundant 

common 

absent 

abundant 
absent 

abundant 
absent 


abundant 
abun-few 
absent 


abundant 
absent 
abundant 
absent 


common 
occasional 


occasional 
common 


common 
common 


rare 
common 


Leitneria 

Liquidambar 

Liriodendron 

Magnolia 

Melia  (Nat.) 

Mohrodendron.  . 

Morus 

Nyssa 

Olneya 

Ostrya 

Oxydendrum 

Parkinsonia 

Paulownia  (Nat.) 

Persea 

Planera 

Platanus 

Populus 

Prosopis 

Prunus 

Ptelea 

Pyrus 

Quercus  (white) . , 

(red).... 

(live) 

Rhamnus 

Rhizophora 

Rhododendron . . 

Rhus 

Robinia 

Salix 

Sambucus 

Sapindus 

Sassafras 

Swietenia 

Symplocos 

Tilia 

Toxylon 

Ulmus 

Umbellularia 

Vaccinium 

Viburnum 

Xanthoxylum 


Tyloses 


absent 
common 


few 

absent 

abundant 

absent 

common 

absent 

abundant 
common 

absent 
few 

common 
absent 

common 
absent 
abun-few 
few-abun. 

absent 

absent 
abundant 
abundant 
common 

absent 

common 

absent 


abundant 
few-abun. 
absent 


common 
occasional 


common 


common 
occasional 


142  ECONOMIC   WOODS   OF   THE    UNITED    STATES 


RING-POROUS   AND    DIFFUSE-POROUS   WOODS 

There  are  36  indigenous  genera,  exclusive  of  shrubs  and  vines,, 
with  ring-porous  woods,  at  least  in  part,  and  4  that  have  become 
thoroughly  naturalized  in  the  United  States.  These  40  genera 
are  representatives  of  20  families  of  which  only  four,  each  con- 
sisting of  a  single  genus,  are  exclusively  ring-porous.  Sixteen  of 
these  genera  supply  wood  of  more  or  less  economic  importance. 
In  the  case  of  Quercus  the  live  oaks  are  mostly  diffuse-porous, 
while  one  species  of  Hicoria  and  one  or  two  of  Ulmus  are  rather 
intermediate,  at  least  in  certain  instances.  Some  species  of  Prosopis 
are  diffuse-porous  and  some  other  genera,  e.g.,  Leitneria  and 
Ptelea,  produce  woods  which  require  rather  close  observation  to 
note  their  ring-porous  nature. 

There  are  35  families  whose  indigenous  representatives  are- 
exclusively  diffuse-porous.  Eleven  of  these  families  include  15 
genera  of  economic  woods.  Of  a  total  of  147  indigenous  dicotyle- 
donous woods,  113  or  nearly  80  per  cent  are  diffuse-porous.  Inso- 
far as  the  economic  woods  are  concerned,  however,  the  division  is. 
about  equal. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES 


143 


TABLE  XII 

Families  with  Indigenous  Representatives  Exclusively 
Diffuse-porous 


Aceracese 

Aquifoliacese 

Betulaceae 

Boraginaceae 

Burseracese 

Canellaceae 

Capparidaceae 

Caprifoliaceae 

Caricaceae  (?) 

Celastracese 

Combretaceae 


Cornaceae 

Cyrillaceae 

Ericaceae 

Euphorbiaceae 

Hamamelidaceae 

Hippocastanaceae 

Koeberliniaceae 

Magnoliaceae 

Myricaceae 

Myrsinaceae 

Myrtaceae 

Nyctaginaceae 


Platanaceae 

Polygonaceae 

Rhamnaceae 

Rhizophoraceae 

Rosaceae 

Salicaceae 

Styraceae 

Symplocaceae 

Theaceae 

Theophrastaceae 

Tiliaceae 

Zygophyllaceae 


TABLE  XIII 

Indigenous  Ring-porous  Woods 


Acacia 

Ailanthus  (Nat.) 

Asimina 

Avicennia 

Broussonetia  (Nat.) 

Bumelia 

Castanea 

Castanopsis 

Catalpa 

Celtis 

Cercis 

Chilopsis 

Chionanthus 


Cotinus 

Dalea 

Diospyros 

Ehretia 

Eysenhardtia 

Fraxinus 

Fremontodendron 

Gleditsia 

Gymnocladus 

Hicoria  (Carya) 

Leitneria 

Melia  (Nat.) 

Moms 


Paulownia  (Nat.) 

Parkinsonia 

Pinckneya 

Prosopis 

Ptelea 

Que  re  us 

Rhamnus 

Rhus 

Robinia 

Sapindus 

Sassafras 

Sophora 

Toxylon 

Ulmus 


144 


ECONOMIC   WOODS    OF   THE    UNITED    STATES 


TABLE  XIV 
Nature  of  Pitting  in  Wood  Fibres  of  Indigenous  Woods 


Acacia 

Acer 

JSsculus 

Ailanthus  (Nat.) 

Alnus 

Amelanchier 

Amyris 

Andromeda 

Anona 

Arbutus 

Arctostaphylos 

Asimina 

Avicennia 

Betula 

Broussonetia  (Nat.). 

Bumelia 

Bursera 

Carpinus 

Castanea 

Castanopsis 

Catalpa 

Ceanothus 

Celtis 

Cercis 

Cercocarpus 

Chilopsis 

Chionanthus 

Chrysophyllum 

Cladrastis 

Cornus 

Cotinus 

Crataegus 

Cyrilla 

Diospyros 

Eucalyptus  (Int.).  •  • 

Fagus 

Ficus 

Fraxinus 

Fremontodendron. . . 

Gleditsia 

Gordonia 

Guaiacum 

Gymnocladus 

Hamamelis 

Hicoria  (Carya) 
Ilex 


Smi*»     derTd 


Juglans 

Kalmia 

Leitneria 

Liquidambar 

Liriodendron 

Magnolia 

Melia 

Mohrodendron. . .  . 

Morus 

Myrica 

Nyssa 

Ocotea 

Olneya 

Ostrya 

Oxydendrum 

Parkinsonia 

Paulownia  (Nat.). 

Persea 

Planera 

Platanus 

Populus 

Prosopis 

Primus 

Ptelea 

Pyrus 

Quercus 

Rhamnus 

Rhizophora 

Rhododendron.. . 

Rhus 

Robinia 

Salix 

Sambucus 

Sapindus 

Sassafras 

Sideroxylon 

Swietenia 

Symplocos 

Tilia 

Toxylon 

Ulmus 

Umbellularia  .... 

Vaccinium 

Viburnum 

Xanthoxylum. . .  . 


Bor- 
dered 


Arrows  indicate  transitions  from  the  prevailing  type. 


ECONOMIC   WOODS   OF   THE   UNITED   STATES 


145 


TABLE  XV 
Kinds  of  Rays  in  Indigenous  Dicotyledonous  Woods 


Genus 

Homo- 
geneous 

Hetero- 
geneous 

Genus 

Homo- 
geneous 

Hetero- 
geneous 

X 
X 

X — 

X 
X 

X 
X 
X 

X 
X— 

X 
X— 

X 

X 

X— 
X 
X— 

X 

X 

Ailanthus  (Nat.) 

X 
X 

X 
X 
X 

Liquidambar 

Liriodendron 

X 
X 

X 

Melia  (Nat.) 

X 

Mohrodendron 

Morus 

X 

X 

X 

X 

X 

I 

X 

X 
X 
X 

— X 

X 

Arctostaphylos 

X 

X 

Olneya 

X 

Broussonetia  (Nat.)... 

X 

Paulownia  (Nat.) 

X 

X 

X 

< X 

X > 

X 
X 

X 
X — 

X 
X 

X 

— X 

X 

X 
X 

Celtis 

— X 

Ptelea 

— X 

Chrysophyllum 

X 

Rhododendron 

X 

X 

Cyrilla 

1   x 
1   x 

< X 

X 

Eucalyptus  (Int.) 

Fagus 

X 

X 

X 
X 

X 

X 
X 

X 
X 

1     X 

X 

X 

Tilia      .          

1 

Umbellularia 

Gymnocladus 

X 

X 

Hicoria  (Carya) 

Ilex 

X > 

1     X 

Xanthoxylum 

X 

Arrows  indicate  transitions  from  the  prevailing  type. 


146 


ECONOMIC   WOODS   OF   THE    UNITED    STATES 


TABLE  XVI 
Indigenous  Woods  with  "Ripple  Marks 


Species 

No.  per  inch 

Remarks 

58-68 

200 

120-128 

200 

150-160 

110-115 

120 

150 
55-80 

250 

150-160 
50-55 

160 
45-55 
55-80 
5.5-60 
55-60 

Artemisia  tridentata 

Baccharis  sarathoides 

Biglovia  graveolens 

Shrub;  rays  not  storied 
Many  rays  2-storied 

Crescentia  curcubitina 

Dalbergia  brownei 

Lines  irregular 
Shrub;  marks  visible 
Rays  not  storied 
Lines  usually  wavy 

Diospyros  virginiana 

Distinct  only  in  inner  bark 
Often  irregular 
Rays  not  storied 
Often  absent 

Sophora  secundiflora 

Swietenia  mahagoni 

it           ti           a 

PROPERTY  LIBRARY 
N.  C.  State  College 


INDEX 


Abies 23,  29,  30,  45,  64, 127 

amabilis 52,80 

balsamea 17,52,  80 

concolor 17,  52,  80 

grandis 17,  52,  80 

magnifica 52,  80 

nobilis 52,80 

Acacia.  .  .  .68,  135,  141,  143,  144,  145 

Acer  7,  27,  40,  43,  44,  47,  64,  66,  129, 

135,  138,  141,  144,  145 

macrophyllum 102 

negundo 52,102 

californicum 102 

nigrum 102 

rubrum 20,  37,  51,  103 

saccharinum 37,  103 

saccharum 37,  47,  51, 102 

Aceracea? 

36,  129,  134,  135,  138,  139,  143 

jEsculus  7,  15,  22,  24,  25,  27,  40,  47, 

64,  129,  135,  138,  141,  144,  145,  146 

calif  ornica 51,  107 

glabra 52,107 

octandra 39,107 

Aggregate  rays 27 

Ailanthus 

7,  135,  138,  141,  143,  144,  145 

Alder 107,129 

Algaroba 91 

Alnus  7,  26,  51,  105,  107,  129,  136, 

139,  141,  144,  145 

Amelanchier. .  .135, 138, 141,  144,  145 

Amyris 135,  141,  144,  145 

Anacardiaceae 135,  138,  139 

Andromeda 136,  138,  144,  145 

Angiosperms 6,  11,  127,  129 

Annual  rings 40-43 

Annular  ridge 134 


Anona 8,135,144,145 

Anonaceae 135,  138,  139 

Appendix 127 

Apple 104 

Aquifoliacese 

128,  129,  136,  138,  139,  143 

Araliacese 139 

Arborvitae 84 

Arbutus  135,  137,  138,  141,  144,  145 
Arctostaphylos 

135,  137,  138,  141,  144,  145 

Arizona  white  pine 76 

Aronia 138 

Artemisia 146 

Ash 92,93,  129 

Asimina  8,  52,  135,  138,  141,  144,  145 

Aspen 108 

Avicennia 141,  143,  144,  145 

Axyris 133 

Baccharis 146 

Bald  cypress 82 

Balsam  fir 79,80 

Bark 5,  8-10,  127 

Basswood 106,  129 

Bast  fibres 8,  66 

Bay 106 

poplar 105 

Beech 101,  129 

Betula  7,  10,  15,  27,  37,  43,  64,  66, 
68,  129,  136,  139,  141,  144,  145 

lenta 37,  51,  65,  103 

lutea 37,  51,  103 

nigra 20,  37,  51,  103 

papyrifera 37,  51,  104 

populifolia 37,  104 

Betulaceaa 

36,  129,  134,  135,  138,  139,  143 
147 


148 


INDEX 


Big  shellbark  hickory 95 

Biglovia 146 

Bignoniacese 

128,  129,  134,  135,  138,  139 

Bigtree 81 

Birch 103,  129 

Bitternut  hickory 95 

Black  ash 93 

birch 103 

cherry 102,  129 

gum 105 

jack  oak 87 

locust 129 

maple 102 

oak 87 

spruce 79 

walnut 96 

willow 99,  108 

Blue  ash 94 

beech 99 

gum 98 

Boraginacese 135,  138,  139,  143 

Bordered  pits 16,  31-35,  131 

Boxelder 99 

Broadleaf  woods 7,  17,  85 

Brousonnetia  138,  141,  143,  144,  145 

Brown  ash 93 

"  cottonwood" 108 

Buceras 135 

Buckeye 107,  129 

Bull  pine 76 

Bumelia 135,  141,  143,  144,  145 

Bur  oak 88 

Bursera 135,  141,  144,  145 

Burseraceae 135,  139,  143 

Butternut 96 

Buttonball 100 

Cactace^e 135 

Caesalpina 65 

Caesalpinese 30 

Calcium  oxalate 21 

California  black  oak 87 

buckeye 107 

laurel 98 


Calif ornia  nutmeg 85 

walnut 96 

white  pine 76 

Cambium 11,12 

Camphor  trees 68 

Camphora 68 

Canella 134 

Canellaceae 139,  143 

Canoe  cedar 84 

Capparidaceue 135,  139,  143 

Capparis 135 

Caprifoliacese 135,  136,  139,  143 

Caricacese 143 

Carpinus,  9,  26,  41,  51,  99,  135,  138, 
139,  141,  144,  145 
Carya  (see  Hicoria) 

Case-hardening 58 

Castanea  20,  40,  47,  48,  52,  68,  69, 
129,  135,  139,  141,  143,  144,  145 

dentata 57,  86 

pumila 51,  86 

Castanopsis  51,  86, 129, 135,  139,  141, 
143,  144,  145 

Cat  spruce 79 

Catalpa  44,  64,  68,  92,  129,  135,  138, 
141,  143,  144,  145 

bignoniodes 92 

catalpa 52,  92 

speciosa 52,  92 

Ceanothus 135,  138,  144,  145 

Cedar 82,  83,  127 

elm 90 

-like  woods 127 

Cedrus 80 

Celastracese 139,  143 

Cell  wall 130 

Celtis  20,  25,  27,  44,  45,  51,  129,  135, 
138,  141,  143,  144,  145 

mississippiensis 89 

occidentalis 89 

Cercidium 67,  135,  141 

Cercis.  .  .135,  138,  143,  144,  145,  146 
Cercocarpus.  .135,  138,  141,  144,  145 

Cereus 135 

Chamaecyparis 64,  80,  127 


149 


Chamaecyparis  Iawsoniana  20,  52,  67, 
68,  69,  83 

nootkatensis 51,  68,  83 

sphseroidea 85 

thyoides 20,  68,  85 

Checking  of  wood 56 

Cheiranthodendrae 138 

Cheirodendron 134 

Cherry 102,  129 

birch 103 

Chestnut 86,  129 

oak 88 

Chilopsis 141,  143,  144,  145 

Chinquapin 86,  129 

chestnut 86 

oak 88 

Chionanthus 135,  138,  143 

Chrysobalanus 135 

Chrysophyllum. .  .  .  135,  140,  144,  145 

Cinnamomum 68 

Cladrastis  64,  96,  135,  141,  144,  145 

Chlorophora 65 

Cliftonia 136 

Chilopsis 135 

Coccolobis 135 

Coffee  tree 92,  129 

Color  of  wood 64-66 

Colubrina 135 

Combretaceae 135,  143 

Common  catalpa 92 

Compositse 133 

Composite  perforations 133-4 

" Compression  wood" 77 

Condalia 50,  135 

Conductivity 62 

Conifera: 6,  127 

Conjugate  cells 25 

Conocarpus 135 

Cork 9,    10 

cambium 9 

Cornacese 129,  136,  139,  143 

Cornus, 

7,  15,  100,  129,  136,  141,  144,  145 

florida 51,  101 

nuttallii 101 


Cortex 8 

Corylus 136,  139 

Cotinus,  135,  138,  141,  143,  144,  145 

Cottonwood 99,  108,  129 

Cow  oak 88 

Crataegus.  51,  128,  135,  141,  144,  145 

Crescentia 135,  146 

"Cross-field" 74 

Crystals 9,  19,  21 

Cuban  pine 77 

Cucumber  tree 106,  129 

Cupressus 51,  127 

Cypress 82,  127 

Cyrilla 136,  144,  145 

Cyrillacea; 136,  139,  143 

Dalbergia 146 

Dalea 135,  143 

Density 49-52 

Dicotyledons,  7,  13,  14,  21,  30,  41,  61, 
85,  127,  128,  129 

Didymopanax 134 

Diffuse-porous  woods, 

16,  43,  95,  142-3 

Diospyros  21,  22,  39,  51,  64,  94,  129, 

135,  141,  143,  144,  145,  146 

Dipterocarpese 30 

Dogwood 129 

Douglas  fir 78,  127 

pine 78 

spruce 78 

Drimys 14 

Drying  of  wood 53 

Dryobalanus 68 

Drypetes 135 

Ducts,  gum 30 

resin 9,  23,  29-31,  78 

Dyewoods 65 

Eastern  hemlock 81 

Ebenaceaj. . .  .  128,  129,  134,  135,  139 

Ehretia 135,  138,  143 

Elements  of  wood 13,  131 

Elm 89,  129 

Epidermis 8 


150 


INDEX 


Epithelial  cells 22,  78,  132 

Ephedra 134 

Ericaceae.  135,  136,  137,  138,  139, 143 
Eucalyptus.  .47,  57,  98,  141,  144, 145 

Eugenia 136 

Euphorbiacea? 135,  139,  143 

Evergreen  oak 98 

Exothea 135 

Eysenhardtia 135,  143 

Fagace^ 129,  134,  135,139 

Fagara 66,  135 

Fagus  7,  9,  20,  26,  43,  44,  47,  51,  66, 
100,  101,  129,  134,  135,  141,  144, 
145 

False  rings 41 

Fascicular  cambium 12 

Fibres 13,  18-20,  88 

Fibre-saturation  point 54 

tracheids 132 

Fibrous  elements 13,  131 

Fibro-vascular  bundles 7,  12 

Ficus 141,  144,  145 

Fir 80,  127 

Five-leaved  pines 74 

Flowering  dogwood 101 

Foxtail  pines 75,  78 

Fraxinus  7,  25,  27,  40,  44,  47,  48,  64, 
129,  141,  143,  144,  145 

americana 22,  51,  94 

lanceolata 51,  94 

nigra 22,  93 

oregona 51,  93 

pennsylvanica 51,  94 

profunda 94 

quadrangulata 51,  94 

Fremontodendron 

138,  141,  143,  144,  145 

Fusiform  rays 25,  29 

Fustic 65 

Giant  arborvit^e 84 

sequoia 81 

Gleditsia  15,  51,  92,  129,  135,  138, 
141,  143,  144,  145 


Gloss 66-67 

Gordonia 136,  140,  144,  145 

Grain 46-48 

Gray  birch 104 

Green  ash 94 

Growth  rings 16,  40-43 

Guaiacum  15,  50,  66,  97,  135,  138, 
141,  144,  145,  146 

Gum 15,  140-1 

ducts 30 

-wood 105 

Gymnocladus  7,  15,  44,  47,  51,  92, 

129,  135,  141,  143,  144,  145 

Gymnosperms  6,  7,  11,  13,  16,  25,  31, 

38,  40,  43,  61,  73,  127,  129 

Hackberrt 89,  129 

Hackmatack 79 

Haematoxylon 65 

Hamamelidacese 

129,  136,  138,  139,  143 

Hamamelis 136,  141,  144,  145 

Hard  maple 102 

-woods 7,  85 

Hardy  catalpa 92 

"Hazel" 105 

Heartwood 6,  44-45,  64 

Helietta 135 

Hemlock 32,  80,  127 

Heterogeneous  rays 24,  25,  145 

Heteromeles 135 

Hickory 92,  95,  129 

elm 89 

Hicoria  2,  21,  22,  44,  66,  129,  135, 141, 
142,  143,  144,  145 

alba 20,  50,  57,  95 

aquatica 51,  95 

glabra 51,  95 

laciniosa 10,  51,  95 

minima 95 

myristicsef  ormis 95 

ovata 95 

pecan 95 

Hippocastanaceae 

128,  129,  135,  138,  139,  143 


INDEX 


151 


Holly 100,  129 

Homogeneous  rays 25,  145 

Honey  locust 92,  129 

"Honey-combed"  wood 58 

Hop  hornbeam 99 

Hornbeam 99 

Hydrangea 136 

Hygroscopicity 59-60 

Hypelate 135 

ICTHYOMETHIA 136 

Idaho  white  pine 75 

Ilex  19,  20,  45,  51,  64,  65,  100,  129, 
136,  137,  138,  139,  141,  144,  145 

Incense  cedar 83 

Interfascicular  cambium 12 

Intermediate  fibers 25,  132 

Ironwood 99 

Juglans  7,  8, 15,  21,  65, 129, 135, 141, 
144,  145 

calif  ornica 96 

cinerea 52,  57,  95,  96 

nigra 20,  61,  66,  96 

Juglandacese 134,  135,  139 

Juniper 84,  127 

Juniperus  10,  22,  41,  44,  45,  47,  51,  64, 
68,  80,  84,  127 

barbadensis 84 

virginiana 49,  57,  66,  67,  68,  84 

Kalmia 136,  138,  141,  144,  145 

Kentucky  coffee  tree 92,  129 

Key  to  woods 73 

"Knees"  of  cypress 82 

Knots 48-49 

Kceberlinia 138 

Kceberliniaceae 139,  143 

Krugiodendron 135 

Laguncularia 135 

Larch 78,  127 

Larix 25,  29,  31,  36,  127 

americana 46,  51,  79 

laricina 79 


Larix  occidentals 17,  51,  79 

Laurel  oak 87 

Lauraceae 128,  129,  135,  139 

Leguminosae.,129,  134,  135,  138,  139 

Leitneria  31,  50,  52,  135,  138,  141, 

142,  143,  144,  145 

Leitneriacese 135,  138,  139 

Leucsena 135 

Libocedrus   17,   22,   52,   68,    69,    80, 
83,  127 

Libriform  fibres 131,  132 

Lignumvitae 97 

Lin 106 

Liquidambar  14,  19,  20,  30,  33,  40,  47, 

51,  57,  64, 105, 129, 136,  138, 139, 

141,  144,  145 
Liriodendron  8,  10,  15,  20,  22,  35,  43, 

45,  52,  57,  64,  106,  129,  136,  139, 

141,  144,  145 

Lithospermum 134 

Live  oak 16,  98 

Loblolly  pine 77 

Locust 91,  129 

Lodgepole  pine 76 

Longleaf  pine 77 

Lowland  fir 80 

Luster 66-67 

Lyonothamnus 135 

Lysiloma 135 

Maceration  of  wood 4 

Madura 91 

Magnolia  8,  15,  22,  35,  40,  51,  129, 
136,  137,  138,  139,  140,  141,  144, 
145 

acuminata 15,  20,  51,  106,  135 

glauca 51,  106 

Magnoliacese 

14,  33,  129,  135,  136,  138,  139, 143 

Mahogany 92,  97,  129 

Malus 135 

Maple 63,  102,  129 

Medullary  rays 21,  23 

spots 36 

Meisteria 134 


152 


INDEX 


Melia 138,  141,  143,  144,  145 

Meliacege 128,  129,  135,  138,  139 

Menziesii 134 

Mesquite 91,  129 

Metaxylem 11,  137 

Middle  lamella 130 

Mockernut  hickory 95 

Mohrodendron.  .  ..136,  141,  144,  145 

Monocotyledons 7,  127-8,  129 

Moracea?  128,  129,  134,  135,  138,  139 

Morus  44,  51,  64,  65,  90, 129, 135, 138, 

141,  143,  144,  145 

Mulberry 90,  129 

Multiperf orate  perforations. ...      134 

Myrica 136,  144,  145 

Myricacese 136,  139,  143 

Myrsine 139,  143 

Myrtacese 136,  139,  143 

Negundo 102 

New  Mexico  white  pine 76 

Noble  fir 80 

Non-porous  woods 73 

North  Carolina  pine 77 

Northern  pine 75 

Norway  pine 76 

Nut  pine 75,  78 

Nutmeg 85 

hickory 94 

Nyctaginaceee 139,  143 

Nyssa  8,  45,  47,  57,  64,  99,  129,  136, 
139,  141,  144,  145 

aquatica 105 

biflora 105 

sylvatica 20,  24,  51,  57,  105 

Oak 16,  87,  129 

Ocotea 135,  144,  145 

Odor  of  wood 67-68 

Ohio  buckeye 107 

Oleacea? 129,  135,  138,  139 

Olneya 135,  141,  144,  145,  146 

Opuntia 135 

Oregon  ash 93 

oak 88 


Oregon  pine 78 

Osage  orange 91,  129 

Osmanthus 135,  138 

Ostrya.50,  99,  135,  139,  141,  144,  145 

Overcup  oak 88 

Oxydendrum..l38,  140,  141,  144,  145 

Palms 128 

Paper  birch 104 

Parenchyma.  .19,  21-23,  86,  131,  132 

Parenchymatous  elements 13,  131 

tracheids 17,  27 

Parkinsonia 

67,  135,  141,  143,  144,  145 

Pasania 98 

Paulownia.. .  .138,  141,  143,  144,  145 

Pecan  hickory 95 

"Pecky"  or  "peggy"  cypress. .       82 

cedar 83 

Pencil  cedar 84 

Pepperidge 105 

Pepperwood 98 

Perforations  of  vessels 

14,  15,  131,  133-6 

pit  membranes 34 

Pericycle 8 

Permeability  of  wood 60-62 

Persea 135,  141,  144,  145 

Persimmon 92,  94,  129 

Phelioderm 9 

Phellogen 9 

Philadelphus 136 

Phloem 8,  11,  129 

Physical  properties  of  wood 

2,  5,  49-69 

Picea  25,  27,  29,  31,  36,  45,  52,  64,  77 

79,  127 

alba 52,  79 

canadensis 79 

engelmanni 17,  52,  79 

mariana 79 

nigra 52,  79 

rubens 17,  79 

rubra 79 

sitchensis 17,  52,  79 


INDEX 


153 


Pignut  hickory 95 

Pin  oak 87 

Pinckneya 135,  143 

Pine 74,  127 

Pink  oak 88 

Piiion  pine 75 

Pmus  2,  10,  23,  25,  27,  28,  31,  33,  67, 
68,  69,  79,  127 

albicaulis 52,  74 

aristata 51,  75 

australis 77 

balfouriana 51,  75 

caribaea 77 

cembroides 75 

contorta 76 

cubensis 77 

densiflora 76 

echinata 17,  51,  77 

edulis 17,  51,  26,  75 

flexilis 52,  74 

heterophylla 45,  51,  77 

lambertiana 17,  52,  75 

laricio 76 

mitis 77 

monophylla 51,  75 

monticola 17,  52,  65,  75 

murrayana 17,  38,  52,  76 

palustris 

7,  17,  44,  48,  51,  53,  55,  69,  77 

ponderosa 17,  30,  31,  51,  76 

quadrif  olia 75 

resinosa 17,  27,  34,  51,  76 

strobiformis 74 

strobus 17,  25,  45,  52,  65,  75 

sylvestris 76 

tseda 17,  45,  48,  51,  55,  77 

virginiana 17 

Pith 5,7-8,  127 

flecks 36-37 

rays 21-27,  145 

Pits 15,31-35,  131 

Planera 135,  138,  141,  144,  145 

Plant  food 130 

Platanacea 129,  139,  143 


Platanus 

10,  26,  66,  129,  134,  141,  144,  145 

occidentalis 20,  47,  51,  100 

racemosa 100 

wrightii 100 

Polygonaceae 135,  139,  143 

Poplar 106,  109,  129 

Popple 108 

Populus  2,  7,  15,  25,  45,  47,  64,  67, 
129,  135,  141,  144,  145 

deltoides 20,  108 

grandidentata 20,  52,  108 

heterophylla 20,  52,  108 

tremuloides 52,  108 

trichocarpa 20,  52,  108 

Pores : 15 

Porous  woods 85 

Port  Orford  cedar 86 

Post  oak 88 

Primary  tissues 11,  137 

rays 23 

Procambium 11 

Procumbent  ray  cells 24 

Prosenchyma 131 

Prosopis  15,  51,  64,  65,  91,  129,  135, 
141,  142,  143,  144,  145 

Protoderm 11 

Protoxylem 11,  137 

Prunus  30,  47,  51,  102,  128,  129,   135 

138,  141,  144,  145 

Pseudotsuga  7,  16,  17,  23,  25,  27,   29 

31,  36,  48,  51,  77,  78,  127 

Ptelea.  .135,  141,  142,  143,  144,  145 

"Punk"  ash 93 

Pumpkin  ash 94 

Pyrus 51,  104,  138,  141,  144,  145 

Qtjercus  2,  7,  10,  14,  15,  21,  25,  40, 
47,  48,  50,  67,  68,  129,  135,  139, 
141,  142,  143,  144,  145 

acuminata 88 

agrifolia 50,  98 

alba 20,  45,  47,  51,  88 

bicolor 88 

calif  ornica 87 


154 


INDEX 


Quercus  chrysolepis 50,  9S 

coccinea 20,  51,  87 

densiflora 98 

digitata 87 

falcata S7 

garryana 88 

hypoleuca 95 

imbricaria 51,  87 

laurifolia 51,  87 

lyrata 88 

macrocarpa 42,  51,  88 

marilandica 36,  87 

michauxii 20,  51,  88 

minor 88 

muhlenbergii 88 

nigra 51,  87 

palustris 51,  87 

phellos 51,  87 

platanoides 88 

prinus 6,  51,  88 

rubra 20,  51,  87 

stellata 88 

suber 10. 

texana 50,  87 

velutina 51,  87 

virginiana 20,  98 

wislizeni 98 

Quillaja 134 

Ray  parenchyma 13,  27,  132 

tracheids 13,  27,  76,  80,  132 

Rays 21,  26-28,  145 

Red  alder 97 

ash 94 

birch 103 

cedar 83,  84 

elm 89 

fir 78,80 

gum 105,  129 

hickory 95 

maple 103 

mulberry 90 

oak 87,  141 

pine 27,  34,  76 

spruce 79 


Red-wood 81 

Resin  cells 22-23 

cysts 29 

ducts 9,  23,  29-31 

Resinous  tracheids 17,  74 

Resonance 62-63 

Reynosia 135 

Rhamnaceae 135,  138,  139,  143 

Rhamnus 138,  141,  143,  144,  145 

Rhizophora 135,  141,  144,  145 

Rhizophoracese 135,  139,  143 

Rhododendron  125,  138,  141,  144,  145 
Rhus 

7,  66,  135,  138,  141,  143,  144,  145 

Ribes 135 

Ring,  growth .  . '. 40-43 

-porous  woods 16,  40,  42,  86 

"Ripple  marks" 39,  146 

River  birch 103 

Robinia  10,  19,  35,  40,  44,  45,  51,  64, 
66,  91,  129,  131,  135,  138,  139, 
141,  143,  144,  145 

Rock  elm 89 

maple 102 

oak 88 

Rosa 133,  134,  138 

Rosacea  36,  128,  129,  133,  134,  135, 
137,  138,  139,  143 

Rotholz 77 

Rubiaceae 135,  139 

Rutacea 135,  139 

Salicace.e 36,  134,  135,  139,  143 

Salix  7,  15,  20,  25,  45,  47,  52,  64,  108, 
129,  135,  141,  144,  145 

Sambucus 7,  135,  141,  144,  145 

Sanio's  beams 38 

Santalum 68 

Sapindacese 135,  139 

Sapindus 135,  141,  143,  144,  145 

Sapotaceae 135,  139 

Sapwood 6,  44,  64 

Sassafras  24,  26,  27,  44,  51,  64,  68,  69, 

92,  129,  135,  141,  143,  144,  145 

Saxifragaceae 136 


155 


Scalariform  markings 33 

perforations 15,  133,  135-6 

pits 33,  139,  140 

Scarlet  oak 87 

Scent 67-68 

Scrophulariacese 138 

Seasoning 53 

"Second-growth" 42,  95 

■Secondary  rays 23 

rings 41 

wall 31 

wood 12-13 

Sectioning  wood 2-3 

Segments,  vessel 14,  131,  132-3 

■Semi-bordered  pits 32 

Septate  fibers 18,  132 

Sequoia  10,  22,  23,  29,  47,  64,  66,  80, 
81,  127 

gigantea 81 

sempervirens 17,  23,  52,  82 

washingtoniana 17,  52,  81 

Shagbark  hickory 95 

Shellbark  hickory 95 

Shingle  cedar 84 

oak 87 

Shortleaf  pine 80 

Shrinkage 56-59 

Sideroxylon 135,  140,  144,  145 

Sidonia 134 

Sieve  tubes 8,  129 

Silver  maple 103 

Simaruba 135,  146 

Simarubacese 135,  138,  139 

Simple  perforations 14,  133-5 

pits 28,  31,  131 

Sitka  cypress 83 

spruce 79 

Slash  pine 77 

Slippery  elm 89 

Soft  ash 93 

maple 103 

pine 27,  74 

-woods 7,  73 

Sophora 135,  143,  146 

Sorbus 134,  135,  138 


Sour  gum 105 

Southern  cypress 82 

pine 77 

red  cedar 84 

oak 87 

swamp  white  oak 88 

Spanish  oak 87 

Specific  gravity 49-52 

Spirals 17,76,  77,  132 

Spotted  oak 87 

Spruce 63,  78,79,  127 

Staphylea 136 

Staphylacese 136 

Sterculiaceae 139 

Stinking  cedar 85 

stone  cells 8,9 

Striations 77 

Structural  properties 1,  5,  130 

Styracea? 136,  139,  143 

Substitute  fibres 25,  132 

Sugar  maple 102 

pine 75 

-berry 89 

Swamp  white  oak 88 

Sweet  bay 106 

birch 103 

gum 105 

locust 92 

Swietenia  18,  30,  39,  51,  64,  97,  129, 
135,  141,  144,  145,  146 

Sycamore 100,  129 

Symplocacese 136,  139,  143 

Symplocos 136,  141,  144,  145 


79 

95 

7,  8,  10 

Taste  of  wood 

69 

Taxacese 6,  7,  13,  22,  85,  127 

Taxodium  10,  22,  34,  47,  52,  64,  66, 
68,  80,  82,  127 

Taxus 7,  10,  16,  44,  77,  80,  127 

brevifolia 51,  85 

floridana 51,  85 

Terminal  parenchyma 22 


156 


INDEX 


Tetracentron 14 

Texture 46-48 

Theacete 136,  139,  143 

Theophrastaceae 143 

Thorn  tree 92 

Thuya 22,  68,80,  127 

gigantea 84 

occidentalis 17,  52,  84 

plicata 17,  23,  52,  84 

Tier-like  structure 39,  165 

Tilia  7,  10,  15,  22,  27,  64,  129,  135, 

137,  138,  141,  144,  145 

americana  20,  39,  45,  52,  106,  146 

heterophylla 39,  52,  106,  146 

pubescens 39,  52,  106,  146 

Tiliaceae  129,  134,  135,  138,  139,  143 
Toxylon  34,  51, 138,  141,  143,  144, 145 

Trabecular 38 

Tracheids 13,  15,  16-18,  132 

Traumatic  resin  ducts 30,  32,  80 

Trochodendracese 14 

Trochodendron 14 

Tsuga.10,  22,  27,  29,  34,  45,  64,  127 

canadensis 17,  32,  52,  68,  81 

heterophylla 17,  66,  80,  81 

Torreya 106,  129 

Tumion 16,  51,  77,  80,  85,  127 

Tupelo 105,  129 

Turkey  oak 88 

Tyloses 15,  35,  36,  60,  140-1 

Ulmace^e 135,  138,  139 

Ulmus  7,  25,  27,  48,  68,  129,  135,  137, 
138,  141,  142,  143,  144,  145 

alata 51,  90 

americana 20,  51,  89 

crassifolia 51,  90 

f  ulva 89 

pubescens 51,  89 

racemosa 51,  89 

Umbellularia 135,  141,  144,  145 

Ungnaria 135 

Vaccinium  134,  136,  138,  141,  144, 
145 


Vascular  bundles 11 

elements 13,  131 

Vauquelinia 135 

Verbeniacese 139' 

Vessels..  .13,  14-16,  75,  131,  132-143 

Viburnum 68,  136,  141,  144,  145 

Violet  wood 68 

Walnut 96,  129 

Warping 56-59 

Water  content 52-55 

beech 99 

hickory 95 

oak 87 

Weight  of  wood 49-52 

Western  chinquapin 86 

dogwood 107 

hemlock 80 

larch 79 

pine 75,  76 

red  cedar 84 

soft  pine 76 

white  pine 75 

yellow  pine 30,  31,  76 

White  ash 94 

bay 106 

birch 103,  104 

cedar 84,  85 

elm../. 89 

fir 80 

hickory 95 

mulberry 90 

oak 16,  88 

pine 74,  75 

spruce 82 

walnut 96 

-wood 106 

Willow 108,  128,  129 

oak 87 

Winged  elm 90 

Wood  cells 19,  130 

fibres 13,  18-20 

parenchyma  19,  21-23,  86,  130,  132 

structure 130 

tracheids 13,  16-1& 


INDEX 


157 


Xanthoxylum  ....  65,  141,  144,  145      Yellow  oak 87 


Xylem . 


.5,  11 


Yellow  birch 103 

buckeye 107 

cedar 82,  83 

chestnut  oak 88 

cypress 83 

fir 78 

locust 91 


popular 106 

-wood 96 

Yew 85,  127 

Yucca 128 

Zygia 135 

Zygogynum 14 

Zygophyllaceae 135,  139,  143 


DESCRIPTION   OF   PLATES 

All  photomicrographs  (except  frontispiece)  show  magnification  of  50  diameters 


PLATE   I. 


DESCRIPTION   OF   PLATE   I. 

Map  of  the  United  States  showing  Natural  Forest  Regions. 


PLATE   II. 


DESCRIPTION  OF  PLATE   II. 

Fig.   1. — Taxodium  distichum  (bald  cypress):    cross  section  through  portions 
of  two  growth  rings.     Several  resin  cells  are  visible  near  the  lower  edge. 

Fig.  2. —  Tsuga  canadensis  (eastern  hemlock):     cross  section.     Note  decided 
contrast  between  early  and  late  wood. 

Fig.  3. — Juniperus    virginiana   (red   cedar) :    cross  section    through    median 
portion  of  growth  ring  showing  zonate  arrangement  of  resin  cells. 

Fig.  4. — The  same:    cross  section  showing  very  thin  late  wood ;    also  doubling 
of  the  late  wood,  producing  "false  ring."     Note  small  size  of  tracheids. 

Fig.  5. — Quercus   alba  (white  oak) :    cross  section  showing  small    pores  with 
thin  walls  and  angular  outlines  and  in  broad  band;    large  pores  with  tyloses. 

Fig.  6. — Quercus  rubra  (red  oak) :   cross  section  showing  small  pores  with  thick 
walls  and  circular  outlines,  and  in  narrow  band ;   large  pores  without  tyloses. 


PLATE  II. 


PLATE  III. 


DESCRIPTION  OF  PLATE   III. 

Fig.  1. — Quercus  alba  (white  oak) :  tangential  section  showing  end  of  large  ray 
and  numerous  small  uniseriate  rays,  separated  by  wood  fibres,  and  occasional 
wood-parenchyma  strands. 

Fig.  2. — Ulmus  americana  (American  elm) :  cross  section  showing  the  largest 
pores  in  a  single  row,  the  small  pores  in  wavy  tangential  bands. 

Fig.  3. — Robinia  pseudacacia  (black  locust)-,  cross  section  showing  arrange- 
ment of  pores  and  parenchyma,  and  very  dense  wood  fibres  in  late  wood;  pores  in 
early  plugged  with  tyloses  and  separated  by  abundant  wood  parenchyma  and 
tracheids. 

Fig.  4. — Toxylon  pomiferum  (Osage  orange) :  radial  section  showing  tyloses 
in  vessels;  wood-parenchyma  strands,  tracheids  and  dense  wood  fibres;  and  hetero- 
geneous ray. 

Fig.  5. — Gymnocladus  dioicus  (Kentucky  coffee  tree):  cross  section  showing 
comparatively  large,  thin-walled  pores  in  late  wood. 

Fig.  6. — Gleditsia  triacanthos  (honey  locust):  cross  section  showing  minute, 
thick-walled  pores  in  late  wood.  Growth  ring  limited  by  rather  wide  zone  of  wood 
parenchyma. 


PLATE    III. 


PLATE   IV. 


DESCRIPTION   OF   PLATE   IV. 

Fig.  1. — Hicoria  ovata  (shagbark  hickory):  cross  section  showing  very  thick- 
walled  wood  fibres  and  distinct  tangential  lines  of  wood  parenchyma;    large  pores 

Fig.  2. — Diospyros  virginiana  (persimmon) :  cross  section  showing  rather  in- 
distinct tangential  lines  of  wood  parenchyma;    pores  without  tyloses. 

Fig.  3. — Hicoria  pecan  (pecan  hickory) :  tangential  section  showing  very 
irregular  rays,  three  large  calcium-oxalate  crystals,  and  numerous  wood-paren- 
chyma strands. 

Fig.  4. — Diospyros  virginiana :  tangential  section  showing  fairly  uniform 
rays  in  storied  arrangement.     Crystals  visible,  but  very  small. 

Fig.  5. — The  same;  radial  section  showing  vessel  segments,  heterogeneous 
rays,  wood-parenchyma  strands,  and  wood  fibres  in  storied  arrangement. 

Fig.  6. — Juglans  nigra  (black  walnut) :  radial  section  showing  rays,  large 
vessel  with  tyloses,  wood-parenchyma  strands,  chambered-parenchyma  cells  with 
crystals,  and  wood  fibres. 


PLATE   V. 


DESCRIPTION*   OF   PLATE   V. 

Fig.  1. — Morus  rubra  (red  mulberry):  cross  section  showing  arrangement  of 
pores  in  late  wood,  width  of  rays,  and  presence  of  tyloses  in  large  pores. 

Fig.  2. — Fraxinus  nigra  (black  ash) :  cross  section  showing  isolated  pores  in 
late  wood  not  joined  tangentially  by  wood  parenchyma.  Outer  margin  of  growth 
ring  composed  of  thin  layer  of  wood  parenchyma. 

Fig.  3. — Alnus  oregona  (red  alder) :  cross  section  showing  aggregate  ray  and 
distribution  of  pores. 

Fig.  4. — The  same:  tangential  section  showing  aggregate  ray,  intermediate 
uniseriate  rays,  vessels,  wood  fibres,  and  wood-parenchyma  strands. 

Fig.  5. — Betula  lenta  (sweet  or  black  birch) :  cross  section  showing  size  and 
distribution  of  pores  and  width  of  rays.  Note  wood-parenchyma  cells,  isolated 
or  in  short  tangential  lines. 

Fig.  6. — Ostrya  virginiana  (hornbeam) :  cross  section  showing  size  and 
arrangement  of  pores  and  distribution  of  wood-parenchyma  cells  in  inconspicuous 
tangential  lines. 


PLATE  V 


PLATE  VI. 


DESCRIPTION   OF   PLATE   VI. 

Fig.  1. — Liquidambar  styraciflua  (red  or  sweet  gum):  cross  section  showing 
size  and  distribution  of  pores,  width  of  rays,  and  arrangement  of  wood  fibres  in 
radial  rows. 

Fig.  2. — Liriodendron  tulipifera  (yellow  poplar  or  tulip-tree):  cross  section 
showing  size  and  distribution  of  pores,  and  thin  layer  of  wood-parenchyma  cells 
marking  outer  limit  of  growth  ring. 

Fig.  3.— Magnolia  acuminata  (cucumber  tree):  tangential  section  showing 
vessels  with  scalariform  bordered  pits,  and  the  small  biseriate  rays. 

Fig.  4. — Liriodendron  tulipifera:  tangential  section  showing  vessels  with 
ordinary  bordered  pits,  and  the  comparatively  large  3-5-seriate  rays. 

Fig.  5. — JSsculus  glabra  (Ohio  buckeye) :  cross  section  showing  uniform  dis- 
tribution of  pores  and  rays. 

Fig.  6. — The  same:  tangential  section  showing  very  fine  uniseriate  rays, 
irregularly 


